Published by The Gloyd Group, Inc. Wilmington, Delaware © 2004 by Nestlé Purina PetCare Company. All rights reserved. Printed in the United States of… [629397]

Hemogram Interpretation
for Dogs and Cats
Alan H. Rebar, DVM, PhD
Clinical Handbook Series$50.00

Hemogram Interpretation
for Dogs and Cats
Alan H. Rebar, DVM, PhD
Clinical Handbook Series

Published by The Gloyd Group, Inc.
Wilmington, Delaware
© 2004 by Nestlé Purina PetCare Company.
All rights reserved.
Printed in the United States of America.
Nestlé Purina PetCare Company: Checkerboard Square, Saint Louis, Missouri, 63188
First printing, 1998.
Laboratory slides reproduced by permission of Alan Rebar, DVM, PhD.
Photographs by Terence Roberts Photography.
This book is protected by copyright.
ISBN 0-9678005-1-X

Table of Contents
Introduction…………………………………1
Part I
Chapter 1
Leukocytes in Health & Disease ………………4
Chapter 2
Erythrocytes in Health & Disease …………..15
Chapter 3
Platelets in Health & Disease ……………….27
Part II
Chapter 4
Hemogram Interpretation …………………….33
Chapter 5
Case Studies …………………………………..39
Part III
Table 1.
Hematological Reference Ranges of the
Dog and Cat …………………………………………………. 81
Index of Figures …………………………………………….. 82
Glossary of Terms ………………………………………….. 85
Suggested Reading ………………………………………….. 87
Nestlé PURINA Hemogram Interpretation for Dogs and Cats

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 1Introduction
This monograph, Hemogram Interpretation for Dogs
and Cats , is divided into three parts. Part I is comprised
of Chapters 1 through 3; Chapters 4 and 5 make up Part II.
To maximize its usefulness, each chapter should be read
and studied in sequence. Part III contains a variety of
reference materials and other resources.
Part I (Chapters 1, 2, and 3) is designed to acquaint the
reader with the basic physiology and pathophysiology of
the hematopoietic system of the dog and cat. It is not
intended as an in-depth treatise but rather focuses on those
aspects of hematopoietic physiology which are most usefulin understanding peripheral blood changes in disease.
Part II (Chapters 4 and 5) is designed to develop asystematic approach to the interpretation of peripheralblood data and morphology, and to afford the reader theopportunity to practice this approach on a series of
actual clinical cases. Of necessity, there is some
redundancy between Parts I and II; however, thisredundancy will serve to reinforce the reader’sunderstanding of hematologic pathophysiology and its
relationship to hemogram interpretation.
Part III includes: Table 1. Hematological Reference
Ranges of the Dog and Cat that lists normal blood values;
a full Index of Figures that describes all the photographs
of slides used in this book; a Glossary of Terms that
contains definitions of those words which are underlined
throughout the text ; and, a comprehensive listing of
Suggested Reading on the topic of canine and feline
hematology.
TM

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 3Part I

4 Nestlé PURINA Hemogram Interpretation for Dogs and CatsOverview
From a functional perspective, circulating leukocytes, or
white blood cells (WBC), belong to two systems: the
phagocytic system and the immunocytic system .
These two immune systems are functionally interdepen-
dent. The phagocytic system is comprised of the granulo-
cytes and the monocyte/macrophage continuum. The
immunocytic system is comprised of circulating T and B
lymphocytes. Factors produced by monocytes/macrophages
profoundly influence lymphocyte function and a variety of
lymphocyte products, in turn, influence the function of the
phagocytes.
The phagocytes (ie, granulocytes, monocyte/macrophage
continuum) are the first line of defense against invading
microorganisms; they are attracted to sites of infection and,
by the process of phagocytosis, ingest and destroy bacteria
and other agents on contact. Therefore, the phagocytes can
be thought of as the non-specific immune system .
In contrast, the immunocytic system is the specific
immune system . Its effector cells (ie, T and B lympho-
cytes) are responsible for both the production of humoral
immunity in the form of antibodies directed against specif-
ic antigens as well as cell-mediated immunity in the form
of specific cytokine production.The following paragraphs explore the structure and
function of each system in greater detail.
The Phagocytic System
The Phagocytic Process
The process of phagocytosis has been well studied and
can be divided into several stages.
The initial stage is chemotaxis . In this early phase, all
phagocytic cells are mobile and are being attracted to sitesof inflammation and infection by an increasing gradient ofsmall molecules known as chemotaxins. Among the most
potent chemotaxins are:
Jlipopolysaccharides (components of bacterial mem-
branes),
Jactive fragments of complement,
Jantigen-antibody complexes, and
Jcertain products of lymphocytes.
Once phagocytes have entered an area of inflammation
and infection, they must adhere to the microorganism(s) in
order for the process of phagocytosis to continue.
Adherence
(stage II) occurs more readily if organisms have
been opsonized; that is, coated by antibodies or comple-ment fragments. Phagocytes have receptors on their sur-
faces for such opsonins which facilitates adherence. The
process of opsonization
represents one of the interactions
between the non-specific and specific immune systems;antibodies are produced by immunocytes, phagocytes
attach to those antibodies.
Next, adhered organisms must be internalized
(stage
III). This is accomplished by invagination of the superficialcell membrane and formation of a phagocytic vacuole around
the organism. Almost simultaneously, the cytoskeletal andmicrotubular system of the cell moves the cytoplasmic gran-ules towards the phagocyticvacuoles. Fusion of therespective membranesallows intimate contact
between granule content and
the microorganism, resultingin killing and digestion ofthe microorganism.Chapter 1 : Leukocytes in Health and Disease
Different Circulating Leukocytes Belong to
Different Immune Systems
Non-specific Specific
Immune System Immune System
MM
Phagocytic Immunocytic
MM
Granulocytes B lymphocytes
Mononcytes/macrophages T lymphocytes The Stages of
Phagocytosis
I. Chemotaxis
II. Adherence
III. Internalization

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 5The Granulocytes
Neutrophils
Neutrophils are the
predominant circulating
granulocyte and are easilydistinguished on theperipheral blood film bythe following morphologic characteristics (Fig. 1):
Jround
Jmeasure 12.0 µ to 15.0 µ in diameter
Jabundant pale pink, granular cytoplasm
Jlobed nuclei with deeply staining, condensed chro-
matin
This morphologic appearance provides significant clues
regarding their functional state. The condensed, deeply
stained chromatin suggests a mature nucleus with predomi-
nantly inactive heterochromatin. The pink, granular cyto-
plasm suggests abundant protein but little machinery (cyto-
plasmic blue staining RNA) to produce additional protein.
The circulating neutrophil is a fully differentiated phago-
cyte capable of seeking out, ingesting, killing, and digesting
invading microorganisms. Two forms of granules, specificgranules and lysosomes, fill its cytoplasm. Specific granules
contain substances, such as lactoferrin and cationic pro-
teins, which are involved in bacterial killing. The lyso-
somes contain digestive enzymes, which act to dissolve
organisms once killed.
While the neutrophil is a highly effective bacterial killingmachine, it is somewhat limited by its own high degree of
sophistication and differentiation. Neutrophils are unable to
divide, replenish their granule content, or regenerate sur-face membrane that is lost in internalization during phago-cytosis of organisms. As a result, their lifespan is extremely
short (hours to days).
Although neutrophils primarily function as phagocytes,
it is noteworthy that these cells also function as secretory
cells. Both when fusion of granules with phagocytic vac-
uoles occurs and when effete neutrophils break
down, biologically active molecules are released
into the microenvironment. Among these areprostaglandins, complement fragments, and biologi-
cally active amines. Clearly, by releasing these reg-
ulatory molecules into the environment, neutrophils
(and, indeed, all phagocytes) function as modera-tors of the local and systemic inflammatoryresponse.
Normal peripheral neutrophil counts in dogs
and cats range between 3000/µl to 12,000/µl. In
health, immature neutrophils (band cells) are onlyrarely observed (less than 300/µl when peripheral
white cell counts are normal). Both increases (neu-trophilia) and decreases (neutropenia) in neu-
trophil numbers are clinically significant, particu-
larly in inflammatory diseases. Similarly, relative
increases in band cells (termed a "left shift") are
also extremely important clinically. To understand the
interpretation of peripheral neutrophil numbers it is firstimportant to understand neutrophil kinetics—the dynamics
of neutrophil production, circulation, and utilization within
the tissues.
Neutrophils are produced in the bone marrow, circulate
transiently in the mainstream peripheral blood (the freely
circulating pool), marginate on the blood vessel walls (themarginating pool), and migrate into the tissues. Within the
marrow there are three pools of neutrophils and their pre-
cursors:
1)the proliferating pool, consisting of the dividing
myeloblasts and promyelocytes, and early myelo-
cytes,
2)the maturing pool, consisting of late nondividing
myelocytes, metamyelocytes, and band cells, and
3)the storage pool, consisting of mature neutrophils.
In general, production of a neutrophil from a myeloblast
takes approximately 5 days. The storage pool contains
approximately a 5-day supply of mature neutrophils. In
Fig. 1 Normal circulating neutrophils.Granulocytes
Neutrophils
Eosinophils
Basophils

6 Nestlé PURINA Hemogram Interpretation for Dogs and Catsother words, if white cell production were interrupted on
day 1 and tissue demand, and therefore circulating half-
life, were normal, it would be 5 days (day 6) before a
reduction in neutrophil numbers would be recognized in
peripheral counts. Neutrophils leaving the storage pool
reside in the circulating pool (from which they are collect-
ed when blood is sampled) for only 6 to 8 hours before
marginating and ultimately being drawn into the tissueschemotactically to perform their phagocytic func-tion. For every neutrophil in the freely circulating
pool, there is at least one marginating neutrophil.
When inflammatory foci develop in the tissues,
production of chemotaxins causes increased release
of neutrophils into the blood, shortened circulating
half-life of neutrophils with increased margination,
and increased egress of neutrophils into the tissues.
Because of the large storage pool of marrow neu-
trophils, in most cases of inflammation, the move-
ment of neutrophils into the blood is greater than
the movement of neutrophils into the tissues; the
net effect is peripheral neutrophilia. In a short time,
the marrow storage pool of mature neutrophils is
reduced to the point where increased numbers of
band cells are drawn into the peripheral blood.
Neutrophilia with a left shift (ie, a regenerative left
shift) is the classic acute(active) inflammatory
leukogram of dogs and cats.
Inflammatory foci release not only chemotaxins
but also colony stimulating factors (CSF), which
cause increased production of neutrophils. If the
inflammation is not resolved quickly, marrow pro-
duction of neutrophils will establish a new balance
with tissue demand. Ultimately, the neutrophil
count will return toward normal and the left shift
tends to disappear. The classic chronicinflammatory
leukogram features a normal or near normal neu-
trophil compartment.
In rare cases of severe acute inflammation, tis-
sue demand is so great that egress of neutrophils
from the blood may actually exceed influx of neu-
trophils from marrow. In these instances neu-
tropenia with a left shift (ie, a degenerative left shift)
develops rapidly and is an indication of overwhelming
inflammation. In the dog and cat, this finding warrants a
guarded prognosis. Eosinophils
The eosinophil is named for its distinctive red-orange
(eosinophilic) cytoplasmic granules, which are variably
sized and round in the dog (Fig. 2) and rod-shaped in the
cat (Fig. 3). These granules contain hydrolytic enzymes and
peroxidase (like the granules of neutrophils), as well as a
core of basic proteins that give the granules their strong
affinity for the eosin stain.
Like neutrophils, eosinophils respond chemotactically to
bacterial products and complement fragments. In addition,
they are attracted preferentially to histamine and the
eosinophilic chemotactic factor of anaphylaxis (ECF-A)
released by mast cells, as well as to certain products
released by activated lymphocytes. From a functional per-
Fig. 3 Normal feline eosinophil.
Fig. 2 Normal canine eosinophil (left), reactive lymphocyte (right).

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 7spective, eosinophils are bactericidal in vitrobut the
extent to which they are bactericidal in vivois
uncertain. However, their role in modulating
hypersensitivity reactions is clear; they elaborate
antihistamines (amine oxidases) and
prostaglandins that inhibit mast cell degranulation.
A second major function of the eosinophil is its
role in the control of parasitic infections. Through
antibody and/or complement mediated binding,
eosinophils become fixed to the surface of helminth
parasites and release their granule content into the
microenvironment. Major basic proteins from the
granules cause considerable damage to the parasite
surface, which leads to parasite death.
Eosinophils have a much shorter circulating
half-life than neutrophils (minutes to several hours
as compared to 4 to 8 hours for neutrophils) so
peripheral counts can be quite erratic from sample
to sample. As a result, eosinophilia (an increase) is
only significant when it is persistent over time. The
most accurate interpretation of persistent
eosinophilia is the presence of a systemic hypersen-
sitivity reaction.
Parasitic infections are only associated with per-
sistent eosinophilia if they have a systemic phase.
For example, whipworm infections in dogs, which
are confined to the intestinal tract, do not cause cir-
culating eosinophilia. In contrast, heartworm infec-
tions, where circulating parasites are present, can
cause marked eosinophilia. Other causes of persis-
tent eosinophilias in dogs include systemic mastocy-
tosis, fleabite dermatitis with systemic hypersensi-
tivity, allergic gastroenteritis, allergic bronchitis, and
atopy. In the cat, feline asthma, eosinophilic granulo-
ma complex (systemic, not oral form), systemic mas-
tocytosis, heartworm disease, and allergic gastroen-
teritis should all be considered. In the author’s opin-
ion, eosinopenia (a decrease) is less consistent and
more difficult to interpret than eosinophilia.
Basophils
Basophils (Figs. 4, 5, 6) are only occasionally
observed on peripheral blood films. They are slight-
ly larger than neutrophils with pale lavender cyto-
plasm and truly segmented nuclei. Basophils of
dogs and cats often contain only a few distinctive
deep blue to purple cytoplasmic granules; as a
Fig. 6 Normal feline basophil (left), normal neutrophil (right).
Fig. 5 Normal canine basophil.
Fig. 4 Normal feline basophil.

8 Nestlé PURINA Hemogram Interpretation for Dogs and Catsresult, they may be mistakenly identified as monocytes.
Besides the truly segmented nucleus, which is useful in dif-
ferentiating basophils from monocytes, the frequent obser-
vation of what appear to be small vacuoles in the nucleus—
which are actually basophilic granules overlaying the nucle-
us—are quite characteristic of basophils.
Basophils are not phagocytic. Nevertheless, they play
an essential role in the inflammatory process. Their cyto-
plasmic granules contain histamine and heparin.
Histamine is one of the primary mediators of the acute
inflammatory response, causing increased vascular perme-
ability. Heparin is an anticoagulant that moderates the
inflammatory microenvironment by inhibiting the forma-
tion of fibrin.
Basophilia is only rarely observed; when present, it
almost always occurs in conjunction with eosinophilia.
The Monocyte/Macrophage Continuum
The monocyte/macrophage continuum represents the
second branch of the phagocytic system and is the primary
link between the nonspecific and specific immune systems.
This cell group was previously known as the reticuloen-
dothelial system and includes not only the circulating
monocytes but also the fixed macrophages of the liver,
spleen, brain, and lymph nodes.
Monocytes are the precursors of all macrophages. They
originate in the bone marrow, circulate in the peripheral
blood, and settle out in the tissues where they differentiate
further as needed. Differentiated cells of the
monocyte/macrophage continuum include activated
macrophages, epithelioid cells, and multi-nucleated
inflammatory giant cells. In addition to their role as
phagocytes, macrophages also perform the follow-
ing functions:
Jmodify antigens in such a way that they
can be recognized by immunocytes (anti-
gen processing cells),
Jrelease numerous inflammatory mediators
that recruit neutrophils, other monocytes,
and lymphocytes into inflammatory sites,
and
Jregulate iron stores.
The only cell of the monocyte/macrophage contin-
uum normally seen in the peripheral blood is the
monocyte. The immature nature of the monocyte is
suggested by its morphology ( Fig. 7). The nucleus isirregularly shaped with a lacy to finely granular chromatin
pattern suggestive of a preponderance of active euchro-
matin. Cytoplasm is abundant, often vacuolated, and gray
to blue, which suggests a high content of cytoplasmic
RNA but little protein. Monocytes seen on a peripheral
blood slide are at approximately the same stage of develop-
ment as the marrow myelocyte of the granulocyte series.
In contrast to granulocytes, which are stored in marrow,
monocytes are released immediately into circulation as
they are produced. They have limited immediate phagocyt-
ic capability, but as mentioned above, possess significantpotential to develop into fully armed effector cells once
seeded in tissues.
Historically, peripheral monocytosis has been interpreted
as indicative of chronic inflammation. Cells of the mono-cyte/macrophage continuum were regarded primarily as the
clean-up cells of inflammation that were recruited into
chronic lesions to remove debris after neutrophilic activity
had localized the primary disease process. While the essen-tial clean-up function of the monocyte/macrophage inchronic inflammation is undeniable, we now understandthat these cells have a much greater role in the inflammatory
process. Furthermore, since proliferating monocytes are
released into and accumulate in the peripheral blood rather
than being stored in the marrow, peripheral monocytosis
can occur quite quickly (in as little as 12 hours).
Consequently, the best clinical interpretation of monocytosis
is simply that there is tissue necrosis and a demand for
phagocytosis. Monocytosis can occur in either acute or
chronic inflammation.
Fig. 7 Two normal canine monocytes are at upper right. A normal canine
neutrophil is at bottom for comparison.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 9The Immunocytic System
The immunocytic or specific immune system is com-
prised of the circulating lymphocytes as well as the lympho-
cytes which are found in primary (bone marrow and thy-
mus) and secondary (lymph node, spleen, Peyer’s patches,
and bronchus-associated lymphoid tissue) lymphoid organs.
Cells of the immunocytic system respond specifically to
antigens by undergoing clonal expansion and differentia-
tion into highly specialized effector cells and memory cells.
Effector cells fall into two major classes:
1) T cell lymphocytes, which release a variety of bio-
logically active molecules known as lymphokines
and play a major role in cell-mediated immunity.
2) B cell lymphocytes, which produce immunoglobu-
lins (antibodies) and constitute the humoral
immune system.
T and B cell classes can be further subdivided into a
number of subsets based upon cell surface markers.
T cell subsets include:
Jhelper cells, which are necessary for the full
expression of the immune response,
Jsuppressor cells, which dampen or moderate the
immune response, and
Jnull cells (essentially devoid of surface markers),which include natural killer (NK) cells and K cells.
JNK cells release biologically active molecules
capable of destroying other cells or microor-
ganisms.
JK cells participate in antibody-depen-
dent cytotoxicity.
B cell subsets preferentially produce
immunoglobulins belonging to a particular class:
JIgG JIgD
JIgM JIgE
JIgA
In addition to the obvious interplay among the
lymphocyte classes and subclasses, lymphocytes
also influence and are influenced by phagocytes.
Among the lymphokines
that T and B cells pro-
duce are numerous molecules that are chemotactic
for both granulocytes and monocyte/macrophages.
Some lymphocyte products may influence marrow
production of phagocytes. Opsonization, as previ-
ously discussed, leads to enhanced phagocytosis.
Knowledge of the immunocytic system and itscomplex functions has expanded dramatically in recent
years. The study of lymphocytes and their various roles hasevolved into the science of immunology, a review of whichis beyond the scope of this chapter. Instead, the next sec-tion will focus on circulating lymphocytes and the interpre-
tation of changes in circulating numbers and morphology.
Normal lymphocyte structure and function
Circulating lymphocytes include representatives of T
cell, B cell, and null cell classes. In most species, approxi-mately 70% of circulating lymphocytes are T cells, 10% to
15% are B cells, and the remainder is comprised of null
cells. Normal cells of the various classes cannot be differen-
tiated morphologically using routine Romanowsky hemato-logic stains.
Normal circulating lymphocytes possess the following
morphologic characteristics:
Jround shape measuring 9.0 µ to 12.0 µ in diameter
Jlarge, round, eccentric nuclei with densely stained,
clumped chromatin patterns (Fig. 8)
Jscant, pale blue cytoplasm, usually observable only
on one side of the nucleus
For the most part, circulating lymphocytes are long-lived
“memory cells” which traverse back and forth betweenblood, lymph nodes, and lymph, monitoring for the presence
of antigens to which they have been previously sensitized.
When stimulated by such antigens, lymphocytes undergo
blast transformation or activation. Activation is a normalprocess. However, increased relative or absolute numbers ofactivated lymphocytes (also known as reactive lymphocytes
Fig. 8 Normal small lymphocyte (round nucleus), three neutrophils, and normal
band cell (right).

10 Nestlé PURINA Hemogram Interpretation for Dogs and Catsor immunocytes) indicates antigenic stimulation.
Morphologically, blast transformed lympho-
cytes are generally more heterogeneous than
unstimulated lymphocytes (Figs. 9 through 13).
They are larger than unstimulated lymphocytes
with larger, more lacy nuclei and increased
amounts of deep blue cytoplasm. Morphologically,
activated B lymphocytes cannot be differentiatedfrom activated T lymphocytes. However, fully dif-ferentiated B cells are plasma cells that are mor-
phologically distinct (Fig. 14). Plasma cells have
eccentric round nuclei with coarsely clumped
nuclei, pale perinuclear clear zones (golgi zones),
and abundant deep blue cytoplasm. Plasma cellsare extremely rare on blood films except in cases
of plasma cell tumor (multiple myeloma).
Normal lymphocyte counts are between
1000/µl and 5000/µl in dogs, and in cats the num-
bers may be as high as 7000/µl. Counts of
between 1000/µl and 1500/µl are regarded as mar-ginal lymphopenias. Both lymphopenia and lym-
phocytosis are relatively common clinical occur-
rences.
Lymphopenia in the range of 700/µl to 1500/µl
is most likely a reflection of high levels of circulat-
ing glucocorticoids (ie, a stress reaction) where
increased numbers of lymphocytes marginate
along vessel walls or, in more chronic conditions,
may be lysed. With more marked lymphopenia,
processes which block the normal circulatory pat-
tern of lymphocytes (blood to tissue to lymph andback to blood) must be considered. These include
lymphosarcomas where lymphocytes leaving the
blood become trapped in massively enlargedlymph nodes, or chylous effusions where lymphat-
ic rupture leads to lymphocyte (and protein)
sequestration in the body cavities.
Lymphocytosis occurs in cases of inflammation
with antigenic stimulation, lymphocytic leukemia,
and lymphosarcomas with leukemic events. In
cases of leukemic lymphocytosis, circulating lym-phocytes are almost always abnormal lym-phoblasts. These cells are larger than normal withless intensely stained nuclei containing large
nucleoli. Leukemias are also often accompaniedby marked non-regenerative anemias. In cats,lymphocytosis can also occur physiologically,
Fig. 10 Reactive lymphocyte (lower center), three neutrophils, and a monocyte (top
center).
Fig. 11 Reactive lymphocyte (center) and four neutrophils.
Fig. 9 Blast-transformed (reactive, activated) lymphocyte.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 11where excitement (ie, epinephrine release) causes
increased blood flow, washing marginated lympho-
cytes into the circulating mainstream where they
can be readily sampled and counted. Physiologic
lymphocytosis in cats, with lymphocytes counts as
high as 20,000/µl, has been observed. Lymphocytes,
in these cases, are morphologically normal and
there is no anemia.
Abnormal Leukocyte Morphology
Neutrophil toxicity
Toxicity in neutrophils is seen when circulating
toxins interfere with the development and differen-
tiation of neutrophil precursors in the bone mar-
row. In dogs and cats, toxicity is most commonly
caused by circulating bacterial toxins. However, tis-
sue necrosis, a variety of drugs, and numerous non-
specific toxins such as lead are all capable of inter-
fering with neutrophil development. Toxic neu-
trophils in the blood are best interpreted as indicat-
ing the presence of unspecified systemic toxemia.
Because toxicity indicates maturation arrest, the
stage of development affected may be important in
assessing prognosis or gauging response to therapy.
In cases where both mature neutrophils and band
cells are equally affected, no such interpretation is
possible. However, in cases where mature neu-
trophils are toxic but bands are normal, morpholo-
gy would suggest that the systemic toxemia is
resolving. In contrast, in cases where bands are
toxic but mature neutrophils are normal, morpholo-
gy suggests a worsening condition.
Morphologically, toxic neutrophils exhibit a
variety of alterations that reflect either cytoplasmicor nuclear developmental arrests or both (Figs. 15
through 18). The most common form of toxicity in
dog and cat neutrophils is foamy basophilia of the
cytoplasm. This is a reflection of retention of cyto-
plasmic RNA and failure of the affected cells to
form their normal complement of protein and cyto-
plasmic granules. Döhle bodies, a relatively minor
sign of toxicity in cat neutrophils but a sign of
marked toxicity in dog neutrophils, are simply
intracytoplasmic precipitates of RNA and appear as
blue basophilic cytoplasmic inclusions. Some toxic
Fig. 12 Reactive lymphocyte
Fig. 13 Reactive lymphocyte
Fig. 14 Fully differentiated plasma cell.

12 Nestlé PURINA Hemogram Interpretation for Dogs and Catsneutrophils are extremely large; this is a reflection
of nuclear maturation arrest characterized by fail-
ure of developing cells to divide properly. Bizarre
nuclear shapes and even multiple nuclei also are
indicative of nuclear maturation arrests.
Atypical lymphocytes
“Atypical lymphocyte” is a term used to
describe a heterogeneous group of circulating
cells of the lymphoid series with a variety of either
nuclear or cytoplasmic abnormalities or both.
Atypical lymphocytes are morphologically distinct
from reactive lymphocytes (immunocytes, activat-ed lymphocytes), which are normal antigen-stimu-
lated lymphocytes.
Nuclear and cytoplasmic features determine
atypical classification. Lymphocytes containing
Fig. 16 Giant toxic band with foamy, basophilic cytoplasm and giant, irregular
nucleus.
Fig. 17 Two toxic neutrophils and a toxic band. Note the unusual nuclear shape.
Fig. 15 Toxic band cell with foamy, basophilic cytoplasm

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 13large, angular nucleoli are sometimes classified as
atypical, although these cells may simply be reac-
tive. Lymphocytes with clefted nuclei (Reider-form
nuclei) are considered atypical. The presence of
large, azurophilic cytoplasmic granules in lympho-
cytes is also regarded as atypical (Fig. 19).
The significance of observing atypical lympho-
cytes on blood films is uncertain. Historically, atyp-
ical lymphocytes were thought to indicate viral
infections. We now know that this relationship is
obscure; animals ill from a variety of causes may
have increased numbers of circulating typical lym-
phocytes. The presence of atypical lymphocytes in
the blood should be noted, but no particular inter-
pretation should be made on the basis of this find-
ing alone.
Fig. 18 Two toxic neutrophils with Döhle bodies.
Fig. 19 Atypical lymphocyte

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 15Overview
The primary functions of the erythron, or red
blood cell (RBC), are as follows:
Jto accumulate oxygen at the alveolar sur-
face of the lung,
Jto transport and release it to all the cells of
the body,
Jto replace the released oxygen with the
waste gas, carbon dioxide, and
Jto transport the carbon dioxide back to the
alveolus where it can be removed from the
body via expiration.
To accomplish these functions, mammalian red
cells have evolved into highly sophisticated yet simple
transport vehicles comprised of hemoglobin (a soluble
transport protein) sealed in a protective cell membrane.
This architecture gives the red cells great flexibility, allow-
ing them to circulate through the most tortuous of vascularspaces. The metabolic pathways of red cells, glycolysis andthe hexose monophosphate shunt, serve primarily to main-
tain the integrity of the cell membrane and the hemoglobin
molecule.
In health, circulating red cell mass, and therefore oxygen
carrying capacity, is kept remarkably constant from day to
day and year to year. For each species, red cell
lifespan is finite and preprogrammed. The rate of
production of new red cells, as regulated by circu-lating erythropoietin
levels, is inversely related to
red cell lifespan. In dogs, circulating red cell lifes-
pan is approximately 100 days; therefore approxi-
mately 1% of circulating red cells die and must be
replaced on a daily basis. Cat red cells have a short-
er average lifespan (approximately 80 days); there-
fore, a somewhat higher rate of red cell production
rate is required to maintain normal circulating red
cell mass.
Red cell morphology is also unique for each
species. Dog red cells measure 6.5 µ to 7.0 µ in
diameter, have prominent areas of central pallor,
are uniformly round, and show little variability in
size and shape from cell to cell (Fig. 1). Mean cellvolume (MCV) is 60 femtoliters (fl) to 75 fl. Approximately1% of the red cells are larger than normal and stain with abluish cast on Romanowsky-stained films; these are imma-
ture red cells known as polychromatophils
(Fig. 2). Their
bluish cast is a reflection of their higher content of cyto-plasmic RNA and reduced content of hemoglobin. Normalcanine red cells show moderate tendency to form stacks orrows (rouleau formation).
Feline red cells are smaller than those of dogs, measur-
ing 5.0 µ to 6.0 µ in diameter with MCVs of 40 fl to 55 fl.Central pallor is minimal. The proportion of polychro-Chapter 2: Erythrocytes in Health and Disease
Fig. 1 Normal canine blood film. Scanning magnification. RBCs are uniform in
size, shape, and color and feature prominent central pallor. Red Cell Morphology
Canine Feline
MM
6.5 µ to 7.0 µ in diameter, 5.0 µ to 6.0 µ in diameter
uniformly round
Prominent areas of Minimal central pallor
central pallor
MCV = 60 fl to 75 fl MCV = 40 fl to 55 fl
Moderate rouleau formation Marked rouleau formation

16 Nestlé PURINA Hemogram Interpretation for Dogs and Catsmatophils is higher in cats than in dogs (up to 2% in cats).
This is a reflection of shorter feline red cell lifespan and
therefore greater marrow production and release of reticu-
locytes. There is marked rouleau formation in cats.
Disorders of the erythron are essentially disorders of red
cell mass (ie, total red cell count, hematocrit, and hemoglo-
bin). Red cell mass can be increased ( poly-
cythemia ) or decreased (anemia). The following
paragraphs detail the diagnostic approach to theevaluation of these two broad categories of disease.
Polycythemia
Polycythemia is diagnosed when measures of red
cell mass are increased. Polycythemia can be rela-
tive or absolute.
Relative polycythemia is the result of hemocon-
centration (dehydration) and is by far the most
common form of polycythemia in dogs and cats.
Elevated total protein as well as an elevation in
total red cell count and hematocrit characterize the
condition, which is reversed by returning blood
volume to normal.
Absolute polycythemia is either secondary or
primary. Secondary absolute polycythemia occurs
as a result of increased production of erythropoi-
etin, either appropriately as a compensatory
response to diseases where there is reduced oxy-
genation of the tissues (eg, heart disease or pneu-
monia) or inappropriately in rare cases of renal dis-
ease or renal neoplasia. There are no peripheralblood morphologic abnormalities in secondary
polycythemia. Primary absolute polycythemia is
polycythemia vera , a rare myeloproliferative dis-
order. Polycythemia vera is characterized by
expanded red cell production in the marrow butno morphologic abnormalities in the peripheral
blood. The condition is diagnosed by ruling out
secondary causes of polycythemia and demon-strating normal blood gas values in the face of ele-
vated red cell mass measures.
Anemia
Anemia is one of the most common syndromes
in all of veterinary medicine and is associated with
a wide range of specific diseases. Anemias fall intotwo broad categories: regenerative and non-regen-erative.
Regenerative anemia is characterized by appropriate
bone marrow response with release of increased numbers
of normal immature red cells into the blood. Regenerative
anemia is either the result of blood loss (hemorrhage) or
hemolysis.
In non-regenerative anemia, marrow response is ineffec-
Anemia
I. Regenerative Anemias:
Blood Loss/Hemorrhagic Anemia
Hemolytic Anemias
Immune-mediated hemolytic anemias
Heinz body hemolytic anemia
Infectious hemolytic anemias
Hemobartonellosis
Babesiosis
Hereditary hemolytic anemiaMicroangiopathic hemolytic anemiaMetabolic anemia with spiculated red cells
II. Non-regenerative Anemias:
Maturation Defect Anemias
Nuclear maturation defectCytoplasmic maturation defect
Hypoproliferative Anemias
Due to inflammatory disease
Due to reduced erythropoietin
Myelophthisic anemia
Due to marrow toxicity
Fig. 2 Canine blood film with increased polychromasia. Scanning magnification.
Polychromatophils are bluish and generally larger than mature cells.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 17tive or inadequate and immature red cells are not
released into the blood in sufficient numbers.
Causes of non-regenerative anemia are severaland often require bone marrow examination for
differentiation.
The first step in classifying an anemia as regen-
erative or non-regenerative is evaluation of theperipheral blood film (Figs. 2, 3). Increased num-
bers of polychromatophils on the film suggestsregeneration. Because polychromatophils are larg-
er than mature cells and have less hemoglobin,
MCV may be increased and mean cell hemoglobinconcentration (MCHC) may be reduced.
If significant polychromasia is present, deter-
mining reticulocyte numbers can more accurately
assess regeneration. This is done by mixing a
small amount of EDTA blood with an equal vol-
ume of a vital stain such as new methylene blue.
The mixture is allowed to incubate at room tem-
perature for thirty minutes and then air-dried
blood films are made. The cytoplasmic RNA in
immature red cells is precipitated by the new
methylene blue as a dark blue reticulum. Cells
containing this precipitate are identified as reticu-
locytes (Figs. 4, 5).
In dogs, all cells with reticulum are counted
when determining a reticulocyte count. In cats,three types of reticulocytes may be identified andare distinguished by the amount of reticulum pre-
sent: 1) punctate reticulocytes, which have only focal
precipitates,
2) aggregate reticulocytes, which contain an
extensive network of reticulum, and
3) intermediate reticulocytes, which have interme-
diate amounts of precipitate.
Only aggregate reticulocytes are counted in cats.
Absolute reticulocyte counts are used to judge
whether or not regeneration is present. The num-
ber of appropriate reticulocytes per 1000 total redcells is noted and converted to a percentage. The
Fig. 4 Low magnification of a new methylene blue-stained blood film.
Reticulocytes stand out due to blue-stained reticulum visible at this
magnification. This represents a highly regenerative anemia.
Fig. 3 Higher magnification of Fig. 2. This represents a regenerative anemia with
marked polychromasia. Note the marked separation of RBCs.
Fig. 5 High magnification of Fig. 4. Reticulocytes with precipitated blue reticulum
are obvious. In dogs, all would be counted; in cats, only those with
abundant precipitate (aggregate reticulocytes) would be counted. Several
leukocytes are also present.Absolute Reticulocyte Count Formula
Ë# reticulocytes/1000 RBC
Ëconvert to %
Ëx total RBC count

18 Nestlé PURINA Hemogram Interpretation for Dogs and Catspercentage can then be multiplied by the total red
cell count to obtain an absolute reticulocyte count.
An absolute reticulocyte count of greater than
80,000/µl is indicative of regeneration in both dogs
and cats.
Regenerative Anemias
Blood loss anemia
In hemorrhagic anemias, circulating red cell
lifespan is normal but red cells are lost from the
body due to external bleeding. A history of bleed-
ing or physical findings consistent with blood lossgenerally makes the diagnosis fairly obvious inthese cases. The degree of regeneration in blood
loss anemia is moderate (no more than two tothree times normal) and is a function of the irondepletion that accompanies red cell loss. The avail-ability of iron for incorporation into hemoglobindirectly influences the rate of red cell productionand, therefore, the degree of peripheral reticulocy-
tosis.
Cases of severe or chronic blood loss may actu-
ally be non-regenerative because of the lack of iron.
Iron deficiency anemia, the end stage of blood loss
anemia, is described under Cytoplasmic Maturation
Defects in the section titled Non-regenerative
Anemias of this chapter.
Hemolytic anemias
The essential feature of hemolytic anemias is
shortened red cell lifespan. Hemolysis can occur
intravascularly as the cells circulate or extravascu-
larly within macrophages of the liver and spleen. In
either case, iron is conserved in the body and is
readily available for reincorporation into hemoglo-
bin. As a result, hemolytic anemias are often more
highly regenerative than blood loss anemias with
reticulocyte counts sometimes exceeding three
times normal.
In many forms of hemolytic anemia, there are
specific morphologic indicators of the underlying eti-ology. Included among these are immune-mediated
hemolytic anemias, Heinz body
hemolytic anemia,
infectious hemolytic anemias, hereditary hemolytic
anemia, microangiopathic hemolytic anemia, andmetabolic anemia with spiculated red cells.
Fig. 6 Canine immune-mediated hemolytic anemia. The anemia is highly regenerative
with marked polychromasia. A spherocyte (arrow).
Fig. 7 A second case of canine immune-mediated hemolytic anemia with
numerous spherocytes.
Fig. 8 Feline immune-mediated hemolytic anemia. Spherocytes are numerous but
less obvious due to the lack of central pallor in the normal RBCs.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 19Immune-mediated hemolytic anemias
Immune-mediated hemolysis occurs when
antigen-antibody complexes form on the surface of
circulating red cells. The antibody may be directed
against an antigen in the red cell membrane itself
(autoimmune hemolytic anemia) or against a for-
eign antibody (eg, drug, infectious agent) carried
on or bound to the red cell surface. Regardless of
the site of antibody activity, the antigen-antibody
complex activates complement, which leads either
to intravascular lysis or removal of red cells by
macrophages in the spleen and liver.
Immune-mediated hemolytic anemias are typical
regenerative anemias, characterized by marked
polychromasia and anisocytosis (variable cell size –
Fig. 6). The presence of significant numbers of
spherocytes is a specific morphologic indicator of
immune-mediated hemolysis, although they may
occur in low numbers in other conditions.
Spherocytes are round, smaller than normal,
intensely stained, and lack central pallor (Fig. 7).They are more difficult to recognize in cats than in
dogs because feline red cells are normally fairly
small and lack central pallor (Fig. 8).
Another feature of some immune-mediated
hemolytic anemias is autoagglutination
(three-
dimensional clumping of RBCs).Autoagglutination, the result of true cross-linking
of red cells by antibodies, confirms the diagnosis of
immune-mediated disease.
Autoagglutination must be differentiated from
rouleau formation. This is done by placing a drop of well-mixed EDTA blood on a slide, adding an equal or slightly
larger volume of isotonic saline, coverslipping the mixture,
and evaluating the finished wet preparation under the
microscope ( Fig. 9). If clumping persists, autoagglutination
is present. Rouleau, the result of attraction between red cells
on the basis of surface charge, will be dissipated by the dilu-
tional effect of the saline.
In the absence of autoagglutination, immune-mediated
hemolysis can be confirmed with a direct antiglobulin test(DAT). The DAT is performed by mixing well-washed
suspect red cells with anti-complement and serial dilutionsof commercially available species-specific anti-IgG.
Microscopic evidence of agglutination of red cells confirms
the diagnosis.Heinz body hemolytic anemia
Heinz bodies are masses of precipitated hemoglobin
formed when increased levels of circulating oxidants over-whelm red cell biochemical defense mechanisms and dam-
age globin. The presence of Heinz bodies interferes with
red cell flexibility, reducing red cell lifespan. Cells contain-
ing Heinz bodies are either lysed as they squeeze through
tortuous vascular spaces (intravascular hemolysis) or aretrapped in the spleen and are removed by macrophages
(extravascular hemolysis). Because Heinz bodies oftenbecome attached to the inner red cell membrane, they maybe recognized on peripheral blood films as nipple-like pro-
jections from the red cell surface (Fig. 10). They have the
same staining properties as normal hemoglobin with
Romanowsky stains, but stain a royal blue with new meth-
ylene blue (Fig. 11).
Fig. 9 Saline-diluted wet preparation demonstrating autoagglutination.
Fig. 10 Heinz body hemolytic anemia in the dog. Several red cells with nose-like
projections (Heinz bodies) are present. The leukocyte at left is a band cell.

There are species differences in susceptibility to
Heinz body formation and Heinz body hemolytic
anemia. Dogs are quite resistant to Heinz body
formation; the demonstration of Heinz bodies on
blood films is enough to confirm the diagnosis of
Heinz body hemolytic anemia in dogs.
In contrast, the hemoglobin of cats is easily oxi-
dized and Heinz body formation is quite common.
In fact, even in health, up to 10% of normal feline
red cells contain Heinz bodies. In metabolic disor-
ders such as hyperthyroidism, diabetes mellitus, or
liver disease, the number of red cells with Heinzbodies can increase dramatically (up to 80% orhigher) without the presence of hemolysis or ane-
mia ( Fig. 12 ). In cats, therefore, the diagnosis of
Heinz body hemolytic anemia requires not only
the presence of Heinz bodies but also the presenceof a highly regenerative anemia.
In cats, most cases of Heinz body hemolytic
anemia are caused by the use of oxidant drugs,such as aspirin. In contrast, drug-induced Heinz
body hemolytic anemia in dogs is relatively rare.
The most common cause of spontaneous Heinz
body hemolysis in dogs is ingestion of large
amounts of raw onions, which contain the oxi-
dant, N-propyl disulfide.
Infectious hemolytic anemias
Infectious hemolytic anemias include lep-
tospirosis, hemobartonellosis, and babesiosis.
There are no specific morphologic indicators of
bacterial-induced hemolysis. In contrast, in both
hemobartonellosis and babesiosis, etiologic agents
are seen on peripheral blood films.
Hemobartonellosis
Hemobartonellosis occurs in both dogs and cats.
In dogs, the disease is uncommon and occurs almostexclusively in splenectomized or immunosuppressedpatients. Clinically, canine hemobartonellosis pre-sents as a typical hemolytic anemia with marked
polychromasia and anisocytosis on routine periph-eral blood films. Hemobartonella canis organisms are
seen as chains of small (0.5 µ) basophilic bodies onthe red cell surface ( Fig. 13 ).
In cats, the disease may be primary or may
occur secondarily to primary immunosuppressive
Fig. 11 Canine Heinz body hemolytic anemia, new methylene blue stain. Several
cells with Heinz bodies (upper left). Two reticulocytes with aggregated
reticulum (right center).
Fig. 12 Feline hyperthyroidism. Numerous cells have obvious Heinz bodies
projecting from their surfaces, but anemia is not present.
Fig. 13 Canine hemobartonellosis. The cell at lower right center has several chains
of basophilic organisms on its surface.
20 Nestlé PURINA Hemogram Interpretation for Dogs and Cats

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 21disorders, such as feline infectious peritonitis (FIP) or
feline leukemia virus (FeLV) infections.
Primary feline hemobartonellosis is a typical hemolytic
anemia with all the attendant signs of marked red cell
regeneration (Fig. 14). Agglutination also may be present,
suggesting an immune component to the disease. As in
dogs, Hemobartonella organisms (Hemobartonella felis) are
seen on the red cell surface. They are generally slightly
larger than H. canis, and may be present as chains, individ-
ual basophilic bodies, or ring forms. Splenomegaly is a
common clinical finding in cats with hemobartonellosis.
Primary feline hemobartonellosis responds well to tetracy-
clines with good prognosis for recovery.
Secondary feline hemobartonellosis is far more common
and the prognosis is poor. The anemia is generally non-
regenerative because the marrow is suppressed and cannotrespond. The diagnosis is based on the presence
of large numbers of organisms on blood films.
These are removed with tetracycline therapy, but
this does not resolve the underlying disease.
Because of the close association of hemobartonel-
losis with immunosuppressive viruses, all cases of
feline hemobartonellosis should be tested for
feline immunodeficiency virus (FIV), FIP, and
FeLV.
Babesiosis
Babesiosis is a relatively uncommon tick-borne
hemolytic anemia of dogs. The causative organ-
ism, Babesia canis, is a teardrop-shaped protozoan
measuring 2.0 µ to 2.5 µ in length.
B. canis organisms are found in varying num-
bers within red cells on blood films from affected
animals (Fig. 15). Anemia is often rapid in onsetand can be quite severe and highly regenerative.
There is often an immune-mediated hemolytic
component to the disease; spherocytes may beobserved in significant numbers. There have been
cases reported with low numbers of organisms ini-
tially misdiagnosed as immune-mediated hemolyt-
ic anemia. Inappropriate treatment of these
patients with steroids results in reduced removal
of organisms by splenic macrophages and a con-
commitant buildup of organisms in the blood.
Upon re-evaluation, the organisms are readily
apparent, and a correct diagnosis can be made.
Hereditary hemolytic anemia
Two forms of hereditary hemolytic anemia associated
with glycolytic enzyme deficiencies have been described in
dogs: pyruvate kinase deficiency and phosphofructokinase
deficiency.
Pyruvate kinase deficiency is described in Basenjis and
Beagles, and is characterized as a chronic hemolytic anemia
with extremely high reticulocyte counts. Shortened red cell
lifespan is a reflection of decreased ATP production and
reduced stability of the red cell membrane. Pyruvate kinase
deficiency is generally diagnosed at 3 to 6 months of agewhen the anemia is moderately severe. Hematocrit valuescontinue to decline slowly thereafter as the compensatorycapacity of the marrow deteriorates. The condition may ter-minate in marrow exhaustion, myelofibrosis, or both.
Phosphofructokinase deficiency has been described in
Fig. 14 Feline hemobartonellosis. Several cells near the center have multiple
basophilic Hemobartonella felis organisms on their surfaces.
Fig. 15 Canine babesiosis. The cell (center) has two teardrop-shaped organisms.
A red cell (lower right) with a single organism.

22 Nestlé PURINA Hemogram Interpretation for Dogs and Catstwo Springer Spaniels. The condition is less severe
than pyruvate kinase deficiency, and is character-
ized by moderate chronic hemolysis with superim-
posed episodes of more severe hemolysis associated
with exercise and overheating.
Microangiopathic hemolytic anemia
All of the hemolytic conditions described thus
far have been characterized by either an intrinsical-
ly or extrinsically induced defect in the circulating
red blood cells leading to shortened red cell lifes-
pan. Shortened red cell lifespan can also occur
when normal red blood cells are forced to circulate
through abnormal vascular beds. This is microan-
giopathic hemolysis.
Microangiopathic hemolysis can occur in any
condition where the morphology of capillary beds
is altered, such as: disseminated intravascular coag-
ulopathy, where capillary lumens are distorted by
the deposition of fibrin; hemangiosarcoma, where
there is localized intravascular coagulopathy;
glomerulonephritis, where glomerular tuft architec-
ture can be obliterated; and some cases of cardiac
disease, where blood flow patterns can be markedly
altered. Microangiopathic hemolysis with red cell
fragmentation can also be a feature of heartworm
disease.
In dogs, microangiopathic hemolysis is charac-
terized by the presence of red cell fragments called
schizocytes (Fig. 16); in cats, fragments are rarely
seen. The degree of anemia, and therefore, the
degree of regeneration, is mild to moderate.
Metabolic anemia with spiculated red cells
In dogs, anemias with spiculated red blood cells
are associated with some cases of liver and kidney
disease. These abnormal red cell shapes are proba-
bly caused by abnormal lipid metabolism and sec-
ondary altered plasma free cholesterol/phospholipid
ratios. Abnormal plasma lipids equilibrate with the
lipids in the red cell membrane and spiculated cells
result. Spiculated red cells are less flexible than
normal, thus some degree of hemolysis occurs.
Despite the hemolytic component, these anemias
are complex and generally non-regenerative
because of the inability of the marrow to respond
appropriately.
Fig. 16 Microangiopathic hemolysis in disseminated intravascular coagulopathy
(DIC). Numerous schizocytes.
Fig. 17 Hepatic hemangiosarcoma in a dog. Two acanthocytes (center). A
schizocyte (left). Numerous target cells, which can be precursors to
acanthocytes, are also present. Polychromasia indicates a mildly
regenerative anemia.
Fig. 18 Canine glomerulonephritis. Numerous Burr cells.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 23Spiculated red cells are of two basic types: acanthocytes
and burr cells. Acanthocytes are red cells with 2 to 10
blunt, elongated, finger-like projections on the red cell sur-
face (Fig 17). Burr cells are oval-shaped red cells with ruf-
fled margins (Fig. 18). Although both cell types can be seen
with either liver or kidney disease, generally acanthocytes
are associated with liver disease while burr cells are more
common in kidney disease.
Non-regenerative Anemias
Non-regenerative anemias can be grouped into two
broad categories: maturation defect anemias and hypopro-
liferative anemias. In most cases, bone marrow evaluation
is required to render a definitive diagnosis in either type of
non-regenerative anemia.
Maturation defect anemias
Maturation defect anemias are the result of
acquired bone marrow abnormalities in which
either nuclear or cytoplasmic development of red
cell precursors is arrested. The defect may be in red
cell precursors only or may affect all proliferating
marrow cell lines. The marrow is generally hyper-
cellular; however, since increased numbers of nor-
mal immature RBCs are not released into circula-
tion, erythropoiesis is ineffective.
Nuclear maturation defect anemia
Nuclear maturation defect anemia is relatively
common in cats but quite rare in dogs. Clinically, it
is a mild to severe non-regenerative anemias with
associated leukopenia and thrombocytopenia.
Pancytopenia indicates a marrow disorder involv-
ing all cell lines.
Variable numbers of excessively large, fully
hemoglobinized red cells (macrocytes) are observed
on blood films. If these are numerous enough in the
blood, MCV is elevated while MCHC remains nor-
mal. Occasional abnormal nucleated red cells may
also be observed on blood films (Fig. 19). These are
usually quite large with large immature nuclei but
fully hemoglobinized cytoplasm. This morphology
indicates arrested nuclear development in the mar-
row; these cells are termed megaloblasts.
Peripheral blood film morphology is suggestive
of nuclear maturation defect anemia. However, for
definitive diagnosis, marrow evaluation isrequired. Marrow samples are hypercellular withincreased activity in all cell lines. All cell lines featurearrested nuclear development with normal cytoplasmicdevelopment. Numerous megaloblasts are seen among thered cell precursors ( Fig. 20 ). Granulocytes have normal
cytoplasm but most nuclei are deficient in chromatin andrarely mature past the myelocyte stage. Megakaryocytesare smaller than normal and contain only one to two nuclei
rather than the normal 8 to16.
The most common cause of nuclear maturation defect
anemia in cats is FeLV, which appears to interfere directly
with DNA synthesis. In dogs, nuclear maturation anemia
results from functional folic acid or vitamin B
12deficiency.
These can be true nutritional deficiencies—which is rare inanimals—or drug-induced, resulting in folate block.
Fig. 19 FeLV (peripheral blood film). Two megaloblasts.
Fig. 20 Bone marrow smear from the same case as Fig. 19. A large megaloblast
(right).

24 Nestlé PURINA Hemogram Interpretation for Dogs and CatsChemotherapeutic agents such as methotrexate and dilantin
are known folate antagonists.
Cytoplasmic maturation defect anemia
Cytoplasmic maturation defect anemia is characterized
by normal nuclear development but arrested cytoplasmic
development (ie, lack of normal hemoglobinization). The
main cause in all animals is iron deficiency. Iron deficiency
anemia is the end stage of blood loss.
Iron deficiency anemia is morphologically distinctive,
particularly in the dog. Red cells are smaller than nor-
mal and have exaggerated areas of central pallor. Redcell indices often feature reduced MCV and MCHC.Iron deficient red cells are more fragile than normal;blood films often have significant numbers of red cellfragments ( Fig. 21).
Hypoproliferative anemias
Non-regenerative hypoproliferative anemias are the
most common anemias in domestic animals. In most cases,peripheral blood findings are nonspecific; bone marrow
evaluation is essential for evaluation. Hypoproliferative
anemias fall into four general categories: anemia of inflam-
matory disease, anemia due to reduced erythropoietin,
myelophthisic anemia, and anemia due to marrow toxicity.
Anemia of inflammatory disease
The anemia of inflammatory disease is the most common
of all anemic syndromes. It is a mild to moderate normo-
cytic, normochromic, non-regenerative anemia with no dis-tinctive morphologic features. Diagnosis is pre-sumptive, based upon evidence of inflammatorydisease, including an inflammatory leukogram.Bone marrow findings are supportive and include
granulocytic hyperplasia, mild erythroid hypopla-
sia, plasma cell hyperplasia, and accumulation of
hemosiderin (iron) in marrow macrophages.
Anemia due to reduced erythropoietin
In many cases of end-stage renal disease, ery-
thropoietin production by the kidney is reduced.
This results in normocytic, normochromic, non-
regenerative anemia. In hypothyroid animals,
there are also reductions in circulating erythropoi-etin primarily because of reduced metabolic
demands for oxygen at the tissue level. Once
again, the net effect is normocytic, normochromic,
non-regenerative anemia.
Myelophthisic anemia
Myelophthisic syndromes are conditions in which an
aberrant cell population replaces normal bone marrow.
Aberrant populations may be either benign (eg, fibrocytes
in myelofibrosis) or malignant (eg, leukemia). Because of
marrow replacement, cytopenia of one or more cell lines is
typical in the peripheral blood. Anemias are severe and
non-regenerative. Leukopenia often is also quite severe, but
platelet numbers are more variable.
In most cases, peripheral red cell morphology is unre-
markable. However, in some cases of myelofibrosis in dogs,poikilocytosis is marked. A particular form of poikilocyte,
the dacryocyte, has been associated with myelofibrosis indogs (Fig. 22). Dacryocytes are teardrop-shaped erythro-
cytes.
Whenever a myelophthisic syndrome is suspected (ie,
whenever severe cytopenias are present), a bone marrow
examination is indicated. Marrow aspirates in myeloph-
thisic syndromes may be hypercellular and immediately
diagnostic or hypocellular (dry tap) and nondiagnostic;
therefore, both marrow aspirates and marrow core biop-
sies should be collected in suspected cases. Marrow aspi-
rates from cases of myelofibrosis are always hypocellular.
Anemias due to marrow toxicity
Marrow cytotoxicity can be caused by both infectious
and noninfectious etiologies. Infectious causes include dis-
eases such as canine and feline parvovirus infections, FeLV
Fig. 21 Iron deficiency anemia. Numerous red cells have exaggerated areas of
central pallor; some are smaller than normal. A red cell fragment
(schizocyte—center).

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 25infection, FIV infection, and canine ehrlichiosis. In
addition to direct marrow cytotoxicity, some of
these agents may cause secondary immune-mediat-
ed marrow suppression. Noninfectious causes of
marrow toxicity include a variety of etiologies such
as estrogen toxicity, cancer chemotherapeutic
agents, and ionizing radiation.
The peripheral blood indicator of marrow toxici-
ty is progressive cytopenia of one or more cell lines.
Clinical signs depend upon which cell lines are
affected and how severely. In the case of red cells,
the degree of anemia can be quite severe and is
non-regenerative. Patients with this kind of anemia
are lethargic with extremely pale mucous mem-
branes. Patients with severe thrombocytopenia may
present with bleeding disorders while those with
severe granulocytopenia may be presented because
of secondary inflammatory conditions.
As with myelophthisic syndromes, bone marrow aspi-
rates and core biopsies are required for diagnosis. In acute
marrow toxicity, bone marrow necrosis may be seen histo-
logically. Cytologic signs of acute toxicity in marrow pre-
cursor cells include cytoplasmic vacuolation and basophilia,
nuclear vacuolation, bizarre nuclear shapes, and cytonu-clear dissociation. In marrow toxicity of longer duration,
the principal alteration is hypocellularity; this must be eval-
uated histologically with core biopsies. If the condition is
characterized by hypocellularity of all cell lines, the condi-
tion may be termed an aplastic anemia. Prognosis in thesecases is guarded.
Fig. 22 Myelofibrosis in the dog. A dacryocyte (center and top center) and
numerous ovalocytes.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 27Overview
Platelets are the third cellular component of the periph-
eral blood; yet, they are often overlooked in both quantita-
tive and qualitative peripheral blood evaluation. Since 90%
or more of the bleeding disorders in dogs and cats result
from abnormalities in platelet number or function, the clini-
cal significance of these cells should not be underestimated.
Furthermore, platelets contain a significant number of bio-
logically active molecules that moderate such events as
inflammation, neovascularization, thrombosis, hemostasis,
fibrinolysis, and coagulation.
On routine blood films, platelets are recognized as small
anucleate discoid cytoplasmic fragments containing variable
numbers of purple granules. Ultrastructurally, they are
much more complex. Shape is apparently maintained
through the interaction of a cytoplasmic microtubular coil
and an actin membrane skeleton located beneath the plas-
ma membrane. The plasma membrane has numerous
invaginations, which form the surface-connected canalicu-
lar system (SCCS). Central to the microtubular coil are theprincipal platelet organelles: two types of granules (alpha
and dense), the dense tubular system (DTS), mitochondria,
lysosomes, and peroxisomes. (See Fig. 1)
The plasma membrane and the SCCS are covered by a
glycoprotein glycocalyx to which coagulation factors and
plasma proteins such as immunoglobulins are adhered.Within the glycocalyx are receptors for the various plateletagonists that initiate the stages of platelet activation. The
plasma membrane is rich in phospholipids, which give rise to
prostaglandins and leukotrienes, important molecular media-tors of the inflammatory milieux. The plasma membraneitself is also the main source of platelet factor 3 (PF 3), a
coagulation co-factor.
Both types of platelet granules also contain a host of bio-
logically active molecules that are important to blood clottingand other life processes, and are released during platelet acti-vation. Dense granules are a source of ATP, ADP, serotonin,
and calcium. Alpha granules contain and ultimately releaseplatelet factor 4 (PF 4), von Willebrand’s factor (VWF), fib-rinogen, and coagulation factor V.
The DTS is derived from endoplasmic reticulum and is
the probable site of platelet prostaglandin synthe-
sis. Calcium, an important component in platelet
aggregation, is also stored in high concentrations
in the DTS.
Production of Platelets
Like all circulating blood cells, platelets are
bone marrow derived. The first recognizable
platelet precursor is the megakaryoblast.Megakaryoblasts undergo endomitosis (nuclear
division without cytoplasmic division) to form
megakaryocytes. Megakaryoblasts have a DNAploidy of 2N to 4N. Fully developed megakary-ocytes may have a ploidy of up to 64N. Because
these cells do not divide as they mature, the num-ber of marrow megakaryocytes is relatively low.
However, as they undergo endomitosis theybecome quite large and are easily recognized in
both cytologic and histologic marrow prepara-
tions. Chapter 3: Platelets in Health and Disease
Fig. 1 Ultrastructure of the platelet.ALPHA
GRANULES
Adhesive proteins
•VWF
•thrombospondin
•fibrinogen
Growth modulators
•PF 4•thrombospondin
•TGF-β
Coagulation
factors
•factor V
•HMWK
•factor X1
•fibrinogenDENSE TUBULAR
SYSTEM
•prostaglandin synthesis
•Ca++
DENSE GRANULES
•ATP
•ADP
•Ca++
•serotonin
CYTOPLASMIC
FACTORS
•factor X111MICROTUBULE
COILPLASMAMEMBRANE
•glycoprotein
•plasma proteins
•coagulation factors
•PF 3SURFACE-CONNECTED
CANALICULARSYSTEM
•glycoproteins
•plasma proteins
•coagulation factors
TGF-β: transforming growth factor β HMWK: high molecular weight kininogen
Modified from Plow EF and Ginsberg MH: Molecular basis of platelet function. In Hoffman R, et
al. (Eds): Hematology: Basic Principles and Practice. New York, Churchill Livingstone, 1991, pp
1165-1176.

28 Nestlé PURINA Hemogram Interpretation for Dogs and CatsHow platelets are actually formed from megakaryocytes
remains unclear. The primary site of thrombopoiesis is also
debated. There is some evidence that in some species the
predominant site of platelet formation is in the lung rather
than marrow. However, it is clear that platelet production isregulated by overall platelet mass in the body and not
platelet numbers. A variety of growth factors are involvedin the initial phase of megakaryocytopoiesis, including
granulocyte-macrophage colony-stimulating factor (GM-
CSF), interleukin 3 (IL 3), IL 6, and megakaryocyte
colony-stimulating factor. Differentiation of megakary-ocytes into platelets is also controlled by growth factors,including thrombopoietin, erythropoietin, GM-CSF, and IL
3. Platelets themselves contain biologically active molecules
(eg, PF 4) which inhibit megakaryocyte production, sug-
gesting that there also may be a negative feedback loop
helping to regulate thrombopoiesis.
Platelet Destruction
As with all other circulating cells, the platelet has a finite
circulating lifespan. Dog platelets circulate for approxi-
mately five to seven days while cat platelets survive only a
little more than a day. Cells of the monocyte/macrophage
continuum are responsible for the removal of effeteplatelets. Nearly half are removed by splenic macrophages
and a third by macrophages of the liver.
Platelet Function
The primary role of the platelet is in hemostasis where it
performs three functions:
Jforming the primary platelet plug,
Jserving as a scaffold for the deposition of fibrin,
and
Jinfluencing clot retraction.
In performing these functions, platelets undergo a complex
series of events described collectively as platelet activation.
Although the events of activation can be described sequen-
tially, in reality, the process is a dynamic one with multiple
events occurring simultaneously.
An early step in platelet activation is platelet adherence.
Normally, circulating platelets will not adhere to intact ves-sel walls. However, when endothelial surfaces are compro-
mised, platelets readily adhere to exposed subendothelial
adhesive proteins including collagen, fibronectin, and VWF. Exposure of platelets to thrombin, present as a result of
simultaneous activation of the coagulation cascade, leads toa platelet shape change. Discoid platelets round up anddevelop numerous surface filaments called filopodia. The
net effect is increased surface area, which serves to increasethe likelihood of platelet-platelet interaction that is critical
to platelet plug formation. Exposure to thrombin also caus-es granule secretion. Released ADP recruits other platelets
into the area. Calcium released from platelets probably isimportant in coagulation reactions. Other granule contents
released include: serotonin, which causes vascular contrac-
tion; additional adhesion molecules; promoters and
inhibitors of coagulation; and growth promoters, which
stimulate fibroblastic proliferation and connective tissue
matrix formation.
When fibrinogen binds to activated platelets, aggrega-
tion, the final step in platelet plug formation, occurs.Initially, aggregation is a reversible reaction. However, with
time the process becomes irreversible.
Platelet activation and platelet plug formation interfaces
with the coagulation cascade in multiple ways. The platelet
plug provides an expanded surface upon which the various
enzymatic reactions of the cascade can occur. The bindingof fibrinogen and thrombin to platelet surfaces further facil-
itates coagulation, as does the release of coagulation cofac-tors from platelets at the time of granule secretion. FactorXIII (fibrin stabilizing factor), an enzyme that catalyzes thecross-linking and stabilization of fibrin, is released fromplatelet cytoplasm at the time of granule release. The cross-linking of fibrin in conjunction with the interaction of the
platelet fibrinogen receptor with platelet actin leads to clotretraction, the last step in coagulation.
Platelet Disorders
Platelet disorders fall into two major categories: quanti-
tative abnormalities and qualitative abnormalities.
Quantitative abnormalities include thrombocytosis and
thrombocytopenia. These abnormalities, in particular,
thrombocytopenia, are by far the most important andprevalent, and are covered in some detail below.
Qualitative abnormalities include: hereditary platelet
function defects in von Willebrand’s Disease, Chediak
Higashi Syndrome, and hereditary canine thromboasthenia;
and acquired function defects associated with certain drugtherapies and systemic diseases. Qualitative abnormalities

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 29are diagnosed when other causes of bleeding have
been ruled out. In general, platelet functional
deficits cannot be diagnosed from routine hemato-
logic data and require the performance of special
tests. They are beyond the scope of this text and,
therefore, will not be discussed.
Thrombocytopenia
Thrombocytopenia, or reduction in the number
of circulating platelets, is caused by one of four
mechanisms:
Jincreased peripheral utilization of platelets,
Jincreased destruction of platelets,
Jincreased sequestration of platelets, or
Jreduced platelet production in the bone
marrow.
These are summarized in Fig. 2.
Increased peripheral utilization
Increased peripheral utilization results when there is
increased systemic demand for platelets. This occurs in two
conditions: disseminated intravascular coagulopathy (DIC)
and blood loss.
DIC is a secondary syndrome associated with underly-
ing severe disease. In most cases, the underlying process is
inflammatory, but DIC also occurs in some cases of neopla-
sia, marked tissue necrosis and shock. Regardless of the
inciting cause, DIC is a syndrome where excessive stimula-
tion of the coagulation cascade leads to the peripheral con-
sumption of both coagulation factors and platelets.
Clinically, animals with fully developed DIC often pre-
sent as emergency patients with bleeding disorders.
Subclinical DIC syndromes also occur. Laboratory findings
can include thrombocytopenia, prolonged activated partial
thromboplastin time (APTT) and one step prothrombin
time (OSPT), decreased fibrinogen levels, and elevated fib-
rin split products. When any three of the above laboratory
abnormalities are present, the diagnosis of DIC is con-
firmed. In dogs, an additional laboratory finding may be
the presence of schizocytes on the peripheral blood film.
Schizocytes are rarely seen in cats with DIC.
Thrombocytopenia secondary to blood loss is mild. If
severe thrombocytopenia (platelet counts of 40,000/µl or
less) is seen in association with blood loss, the throbocy-
topenia is probably the cause rather than the result of the
hemorrhage. Increased platelet destruction
Like utilization thrombocytopenia, destruction thrombo-
cytopenia is associated with shortened circulating platelet
lifespan, but in this case, as a result of immune-mediated
removal. As with immune-mediated hemolysis, immune-
mediated thrombocytopenia may be a true autoimmune
syndrome caused by circulating antiplatelet antibodies, or it
may be secondary to drug therapy, infectious diseases, or
neoplasia.
For the general practitioner, the specific diagnosis of
immune-mediated thrombocytopenia can be challenging.
The degree of thrombocytopenia is usually marked, withcounts of 20,000/µl or less. Bone marrow aspirates can be
taken to estimate megakaryocyte numbers. Most cases of
immune-mediated thrombocytopenia are characterized by
increased numbers of megakaryocytes, although rare caseshave reduced numbers. Utilization thrombocytopenia also
has either normal or increased numbers of megakaryocytes.
Clinical signs, history, and other laboratory data, including
coagulation tests, are useful in ruling out utilization throm-bocytopenia, thereby allowing a presumptive diagnosis ofimmune-mediated thrombocytopenia. Special tests forimmune-mediated thrombocytopenia (eg, PF 3 test,antimegakaryocyte antibody test) may be considered,though the value of these tests is controversial.
Once other causes of thrombocytopenia have been ruled
out and a presumptive diagnosis of immune-mediated
thrombocytopenia is made, immunosuppressive therapy can
be instituted. If successful, the therapy itself serves to con-firm the diagnosis.Fig. 2 The four mechanisms of thrombocytopenia.Utilization
• blood loss
• DIC
Destruction
• immune-mediated (primary
or secondary)
Sequestration
• endotoxemia
• hepatomegaly
• hypothermia
• splenomegaly
Production
• intramarrow bone diseasePlatelets

30 Nestlé PURINA Hemogram Interpretation for Dogs and CatsSequestration thrombocytopenia
Thrombocytopenia can occur in cases of hepatomegaly
or splenomegaly as a result of sequestration of platelets in
the enlarged organs. This condition is much more common
in humans than in animals, and is very rare in dogs and
cats. Hypothermia has been demonstrated to cause platelet
sequestration in the liver. Thrombocytopenia in endotox-
emia is believed to be at least partially the result of seques-
tration in the lung.
Hypoproliferative thrombocytopenia
Hypoproliferative thrombocytopenia is the direct result
of reduced megakaryocytopoiesis. In most cases, there is
reduced production of at least one other cell line;
hemograms generally reflect anemia and/or leukopenia in
addition to thrombocytopenia. Bone marrow biopsies
reveal reduced numbers of precursors of each of the affect-
ed cell lines. Both aspirates and core biopsies are usually
required for proper evaluation. The specific cause is often
obscure and may include infectious diseases, drug toxicity
or myelosuppression, myelofibrosis, immune-mediated mar-
row disease, and cancer.
Thrombocytosis
Thrombocytosis is defined as increased numbers of cir-
culating platelets. Clinically, it is much less common than
thrombocytopenia. In the dog and cat, most cases of throm-bocytosis are secondary or reactive. Thrombocytosis can be
seen secondary to splenic contraction (eg, with excitement
or exercise), elevated circulating glucocorticoids, splenecto-
my, or fractures. For the most part, reactive thrombocytosis
is clinically insignificant.
Thrombocytosis also can occur as a feature of several
primary bone marrow diseases. Primary platelet leukemia is
a true myeloproliferative disorder. In the cat, it may beFeLV related. Platelet leukemia can manifest in either oftwo forms: primary thrombocythemia with very high num-
bers of circulating platelets, or megakaryoblastic leukemia
with variable numbers of circulating platelets but massiveproliferation of platelet precursors in marrow and usually
other tissues. In both conditions, platelets with bizarre mor-phology may be seen in the peripheral blood.
Polycythemia vera is a second myeloproliferative disor-
der which can be characterized by thrombocytosis.Polycythemia vera is a stem cell defect which is character-
ized by overproduction of all cell lines. The degree of over-
production is relatively subtle; evaluation of marrow biop-sies generally reveals no abnormalities.
As discussed in Chapter 2, myelofibrosis is a marrow
disorder that can be characterized by either thrombocy-topenia or thrombocytosis. Other presenting features areused to establish the diagnosis; these include marked non-
regenerative anemia, leukopenia, and poikilocytosis withdacryocytes on the peripheral blood film.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 31Part II

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 33Overview
Hemogram interpretation, or evaluation of the peripher-
al blood, is one of the foundations of clinicopathologic
assessment of the sick patient, both from the perspective of
making the initial diagnosis and prognosis, and from the
perspective of monitoring response to therapy. Hemogram
interpretation is an integrated evaluation of the various
tests of the complete blood count (CBC), which consists of
white blood cell data, red blood cell data, and platelet data.
The CBC has both qualitative and quantitative compo-
nents. The qualitative component is the evaluation of blood
cell morphology on the peripheral blood film. The quantita-
tive components include all the numerical measures in the
CBC: total cell counts, white cell differential, hematocrit,
hemoglobin, red cell indices, and total plasma protein.
Accurate hemogram interpretation is based on a clear
understanding of the physiology and pathophysiology of
the various components of the hematopoietic system. In the
previous three chapters, white cell, red cell, and platelet
responses in health and disease were reviewed and illustrat-
ed. This chapter will develop a systematic approach to
CBC interpretation built around this basic information. In
many instances, the reader will be referred to appropriate
pages in the preceding chapters for further detail.
In evaluating the CBC, white cell data are always inter-
preted first, followed by interpretation of red cell data, and
finally platelet data. This order is logical since abnormali-
ties in white cell data may suggest potential red cell and
platelet alterations.
Interpreting the Leukogram
White cell data in the CBC include the total white cell
count, the differential cell counts, and evaluation of white
cell morphology on the peripheral blood film. All cell
counts should be reported in absolute numbers. The prima-
ry value of white cell data is in recognizing and classifying
inflammatory responses. Considered collectively, leukogram
data are used to address the following questions:
1) Is there evidence of inflammation? 2) Is there evidence of a glucocorticoid (stress)
response?
3) Is there evidence of an epinephrine (excitement)
response?
4) Is there evidence of a systemic hypersensitivity
reaction?
5) Is there evidence of tissue necrosis?
6) If inflammation is present, can it be further classi-
fied?
7) Is there evidence of systemic toxemia?
Is there evidence of inflammation?
Reference ranges for total white cell count and differen-
tial cell counts in dogs and cats are found in Table 1at the
back of this book (Part III). The signposts of inflammationare a neutrophilic left shift, persistent eosinophilia, and/or amonocytosis. These can be seen individually or in any com-
bination. Monocytosis and eosinophilia are easily recog-
nized as any value above the reference range. Identificationof neutrophilic left shifts is somewhat more subjective. Left
shifts are usually defined in relationship to total neutrophil
or WBC count. As a guide, if the total white cell count is
normal, a count of greater than 300 bands/µl constitutes aleft shift. If the total white cell count is 25,000/µl to
30,000/µl, at least 1000 bands/µl are required to designate aleft shift. If the total white cell count is below normal,
fewer than 300 bands/µl indicates a left shift.
Based on the above criteria, it should be clear that total
white cell count alone cannot determine whether or notinflammation is present. Inflammation can be present in the
face of low, normal, or high total white cell count. Totalwhite cell count is primarily an indicator of balance
between bone marrow production and two other key fac-
tors; the release of granulocytes and tissue demand for
leukocytes. A normal white cell count indicates that thebalance between marrow production and release of granu-
locytes and tissue utilization is being maintained. Elevated
white cell counts indicate increased bone marrow produc-tion and granulocyte release relative to tissue demand.Reduced white cell counts indicate that leukocytes are mar-ginating along vessel walls and moving into the tissues at
greater rates than they are being produced and releasedChapter 4: Hemogram Interpretation

34 Nestlé PURINA Hemogram Interpretation for Dogs and Catsinto the blood from the marrow. Classification of an inflam-
matory response as active, chronic, or overwhelming
depends upon which of these dynamic states exists. This
will be discussed in greater detail later in this chapter.
Inflammatory responses can also occur without any of
the classic signposts; in these cases the leukograms are
ambiguous. For example, a mild, mature neutrophilia may
be the result of inflammation, however, it also may be dueto other factors, such as high circulating glucocorticoid lev-
els. In these cases, repeat CBCs done at 6- to 12-hour inter-
vals may help clarify the response. In inflammatory dis-
eases, left shifts are comon.
Is there evidence of stress?
The classic stress (glucocorticoid-induced) leukogram
includes: mild, mature neutrophilia, lymphopenia,
eosinopenia, and mild monocytosis. Of these changes, only
the lymphopenia is specific. In dogs and cats, lymphocyte
counts of between 700/µl and 1500/µl are consistent with a
glucocorticoid effect. Lymphocyte counts of less than
700/µl may be partially the result of stress, but other causes
of lymphopenia must be explored. These include lym-
phoma, chylous effusions, and lymphatic obstruction.
When a stress leukogram is present, other alterations in
the hemogram and clinical chemistry panel can be antici-
pated. There may be mild polycythemia as well as mild
inappropriate nucleated red cell response (5 to 10 nucleated
red cells/100 white cells counted). Isosthenuria is a com-
mon finding. Mild hyperglycemia (120 mg/dl to 180 mg/dl)
is typical and there are often mild to moderate elevations in
serum transaminases. If the leukogram is a result of
Cushing’s disease, elevations in alkaline phosphatase (dog
only) may be marked (more than four times the upper
range of normal).
Is there evidence of excitement?
Excitement causes the release of epinephrine; epineph-
rine, in turn, causes increased blood flow. Increased blood
flow washes marginating leukocytes off vessel walls and
back into circulation where they can be collected and
counted. In dogs and cats, under normal circumstances, the
ratio of freely circulating to marginating cells is 1:1.Theoretically, therefore, epinephrine release has the poten-
tial to double the total white cell count. In dogs, excitement
leukocytosis is primarily the result of neutrophilia while in
cats, it is usually the result of lymphocytosis.
Epinephrine-induced leukocytosis occurs as soon asblood flow increases, and disappears just as rapidly when
blood flow returns to normal. This is in direct contrast to
the glucocorticoid response, which takes approximatelyfour hours to develop and lasts for approximately 24 hours.
Is there evidence of a systemic hypersensi-
tivity reaction?
Persistent eosinophilia is not only indicative of inflam-
mation; it is also suggestive of systemic hypersensitivity.
For a more in-depth discussion of the interpretation of
eosinophilia and a listing of possible causes, refer to
Chapter 1, page 6.
Is there evidence of tissue necrosis?
Tissue necrosis is presumed to be present whenever
there is peripheral monocytosis. For a more complete dis-
cussion of monocytosis, turn to Chapter 1, page 8.
If inflammation is present, can it be further
classified?
In dogs and cats, acute or active inflammation is charac-
terized by rapid movement of neutrophils from bone mar-
row to the site of involvement in the tissues. In most cases,
because of the large marrow reserve of neutrophils, the rateof entrance of neutrophils into the blood generally exceeds
the rate of exit into the tissues; therefore, the white cell(neutrophil) count is usually elevated. At the same time,
because of the high demand for neutrophils, immature neu-
trophils (band cells) will also be drawn into the blood.
Thus, neutrophilia with a left shift (a regenerative left shift)
is the typical and appropriate neutrophil response in acute
inflammation. Tissue necrosis is a variable accompaniment,
so monocytosis may or may not also be present. Because
animals with acute inflammatory disease are almost alwaysunder stress, there is almost always lymphopenia.
Occasionally, in acute inflammatory conditions, tissue
utilization is greater than the ability of the marrow to keeppace with demand. This constitutes overwhelming inflam-mation and the prognosis is guarded. In these cases, total
white cell count and neutrophil count are reduced and
there is a left shift (degenerative left shift). Changes in lym-phocyte counts and monocytes are as described above.
If acute inflammation continues unresolved, it gradually
enters a chronic phase with leukogram features to match.
Circulating half-life of neutrophils remains short, but over
time expanded marrow production equilibrates with thehigh turnover rate. Eventually a new steady state is estab-

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 35lished. The net effect is that neutrophil numbers return to
near normal and the left shift disappears. Animals with
chronic inflammatory conditions continue to be stressed
(lymphopenia) but at the same time often have antigenic
stimulation (lymphocytosis). The net effect is a normal to
slightly elevated lymphocyte count. Because of tissue
necrosis and the ongoing demand for phagocytosis, the
most consistent abnormal finding in chronic inflammatory
leukograms is monocytosis.
It is important to note that not all cases of inflammatory
disease have leukograms that fall neatly into these
described patterns. In addition, the separation of responses
into acute and chronic is somewhat arbitrary, as leukogram
data cannot be used to judge the duration of a disease
process. For example, the length of time required for bone
marrow production to equilibrate with tissue utilization will
vary from case to case. Nevertheless, once the presence of
inflammatory disease has been established, certain other
possible hemogram changes should also be considered.
The most common red cell accompaniment to inflamma-
tory disease is anemia. The anemia is mild to moderate and
non-regenerative. In dogs, hematocrits are between 30%
and 40%. In cats, hematocrits may drop to as low as 25%.
Anemia with these features in association with inflammato-
ry leukograms is considered to be the anemia of inflamma-
tory disease. The anemia of inflammatory disease has gen-
erally been regarded as a chronic condition; however, in
cats, it can develop in a week or less. In the dog, slightly
more time is required because of the longer red cell lifes-
pan. See Chapter 2 for more information on anemias.
Inflammatory diseases, particularly chronic ones, are
often associated with increased immunoglobulin production
by the specific immune system. In the hemogram, this is
seen as hyperproteinemia. Hypergammaglobulinemia can
be confirmed by evaluating total protein and albumin in the
serum chemistry panel.
Whenever inflammatory leukograms are present, partic-
ularly if overwhelming or marked, special attention should
be given to platelet numbers. If platelet numbers are
reduced, the possibility of DIC should be considered. The
blood film should be scanned for schizocytes. Completion
of a DIC panel (see Chapter 3, page 29) is indicated.
Is there evidence of sytemic toxemia?
Systemic toxemia occurs when circulating toxins of
either infectious or noninfectious origin interfere with the
differentiation of neutrophil precursors in the marrow. Theresult is the presence of toxic neutrophils on peripheral
blood films. These have been described and illustrated in
detail in Chapter 1. Systemic toxemia is a poor prognostic
sign.
Interpreting the Erythrogram
Red cell tests in the CBC include total red cell count,
hemoglobin, hematocrit, red cell indices (MCV, MCHC),
total protein, and evaluation of red cell morphology on the
blood film. Red cell count, hemoglobin, and hematocrit are
measures of red cell mass or oxygen carrying capacity of
the blood. Total protein provides immediate information
about state of hydration, which can be very important ininterpreting red cell mass. Elevations in total protein aremost commonly the result of dehydration, which can falsely
elevate indicators of red cell mass. The only other commoncause of hyperproteinemia is hypergammaglobulinemia in
inflammation.
As with leukogram data, erythrogram data are best
interpreted by answering a series of questions:
1) Is red cell mass increased (polycythemia),
decreased (anemia), or normal?
2) If increased, is the polycythemia relative or
absolute?
3) If polycythemia is absolute, is it primary or sec-
ondary?
4) If red cell mass is decreased, is the anemia regener-
ative or non-regenerative?
5) If regenerative, is the mechanism blood loss or
hemolysis?
6) If non-regenerative, can the mechanism be deter-
mined without bone marrow evaluation?
Is red cell mass increased, decreased, or normal?
This simple but all-important question is answered by
evaluating the primary indicators of red cell mass (RBC
count, Hb, HCT). Increases indicate polycythemia;decreases indicate anemia.
If increased, is polycythemia relative or absolute?
The combination of elevated hematocrit and elevated
plasma protein is highly suggestive of dehydration and rela-
tive polycythemia. Dehydration can be confirmed on the
basis of history, physical evaluation, and clinical chemistry.Clinical chemistry findings which are supportive of dehy-
dration include elevated blood urea nitrogen (BUN) in

36 Nestlé PURINA Hemogram Interpretation for Dogs and Catsconjunction with concentrated urine specific gravity (prere-
nal azotemia), high normal or elevated albumin, and high
normal or elevated serum electrolytes. In the absence of
such indicators of dehydration, polycythemia is absolute.
If polycythemia is absolute, is it primary or sec-
ondary?
Secondary polycythemia is ruled out first. As suggested
in Chapter 2, polycythemia can be associated with primary
renal disease, cardiovascular or pulmonary disease,
Cushing’s disease, or neoplastic disease of the kidneys,
either primary or metastatic. In the absence of such condi-
tions, polycythemia is considered to be primary (poly –
cythemia vera). Evaluation of arterial blood gas values and
determination of erythropoietin levels will confirm the pres-
ence of polycythemia in the face of normal oxygenation of
the blood and normal hormonal stimulation of the red cell
marrow.
If red cell mass is decreased, is anemia regenera-
tive or non-regenerative?
The first step in classifying an anemia is evaluation of
the peripheral blood film. If there is increased anisocytosis
and polychromasia, the anemia is likely regenerative.
Regeneration can be confirmed by doing a reticulocyte
count; absolute reticulocyte counts of greater than
80,000/µl are indicative of regenerative anemia in both dogs
and cats.
If regenerative, is the mechanism blood loss or
hemolysis?
History, clinical signs, physical examination, and reticu-
locyte count are the first data evaluated in differentiating
blood loss from hemolysis. Most animals with blood loss
anemia have histories of trauma or visible bleeding. History
or clinical signs of vomiting, diarrhea, or marked external
parasitism also are compatible with blood loss.
Hemoglobinuria, hemoglobinemia, or marked retculocyto-
sis (greater than 200,000/µl) are highly suggestive of
hemolysis.
In all cases where blood loss is not clearly the cause of
the regenerative anemia, care should be taken to evaluate
the peripheral blood film for abnormal red cells. The mor-
phologic signposts of hemolysis have been described and
illustrated in detail in Chapter 2; they include spherocyto-
sis, the presence of etiologic agents on red cells (hemobar-tonellosis, babesiosis), the presence of Heinz bodies, and
the presence of schizocytes.
If non-regenerative, can the mechanism be deter-
mined without bone marrow evaluation?
The most common of all anemias in dogs and cats is the
anemia of inflammatory disease. If the anemia is mild to
moderate and there is an inflammatory leukogram, the ane-
mia of inflammatory disease is diagnosed. If there is signifi-
cant renal disease, non-regenerative anemia associated with
lack of erythropoietin is often seen. If there is marked
hypochromasia and microcytosis (indicated by red cell
indices and/or red cell morphology on the blood film, see
Chapter 2), then iron deficiency anemia can be diagnosed.
All other non-regenerative anemias require bone marrow
evaluation for definitive diagnosis. There are, however, syn-dromes where CBC findings and peripheral blood film
morphology can be suggestive of non-regenerative anemia.
These include myelofibrosis, characterized by severe ane-
mia, leukopenia, variable platelet response and dacryocytes
on peripheral films, and megaloblastic anemia where giant
RBCs and even megaloblasts can be seen on peripheralfilms (see Chapter 2).
Interpreting the Thrombogram
The only platelet tests in the routine CBC are evaluation
of platelet numbers and platelet morphology on the periph-
eral blood film. As discussed in Chapter 3, platelet disor-
ders are either quantitative or qualitative. Using the routine
tests in the CBC, only quantitative disorders can be evalu-
ated. The questions to be addressed are the following:
1) Are platelet numbers normal, increased (thrombo-
cytosis), or decreased (thrombocytopenia)?
2) If there is thrombocytosis, is it reactive or primary?
3) If there is thrombocytopenia, can the mechanism
be determined?
Are platelet numbers normal, increased, or
decreased?
The answer to this question is, of course, based on
platelet count, with a note of caution: automated plateletcounts in cats are often inaccurate because of plateletclumping and the overlap of platelet and red cell sizes.Particularly in cats, platelet numbers should be estimated
from blood films (adequate versus low) as well as counted

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 37in an automated system. If discrepancies exist between esti-
mates and automated counts, hand counts using Unopette®
(Becton-Dickinson, Rutherford, NJ) methods should be
completed. In general, extended hematocrit methods are
more accurate at determining platelet counts in cats than
are impedance methods.
If there is thrombocytosis, it is reactive or
primary?
Reactive or secondary thrombocytosis is by far most
common. Reactive thrombocytosis is discussed in Chapter
3, page 30. When causes of reactive thrombocytosis have
been ruled out, primary thrombocytosis due to platelet
leukemia must be considered. Bone marrow biopsies will
probably be required for confirmation but platelet mor-
phology on the blood film should be closely scrutinized. In
most platelet leukemias, bizarre platelets are seen in the
peripheral blood.
If there is thrombocytopenia, can the mechanism
be determined?
Thrombocytopenic mechanisms are discussed in detail in
Chapter 3 and are merely summarized here from a diagnos-
tic perspective.
Thrombocytopenia in conjunction with inflammatoryleukograms and the presence of schizocytes and neu-
trophil toxicity on blood films is suggestive of utilization
thrombocytopenia associated with DIC. The DIC panel
should be run for confirmation (see Chapter 3). The pos-sibility of sequestration thrombocytopenia is suggested by
clinical evidence of hepatosplenomegaly. Destruction(immune-mediated) thrombocytopenia may be found inassociation with immune-mediated hemolytic anemia(highly regenerative spherocytic anemia) or without other
hematologic abnormalities. Evidence of megakaryocytic
hyperplasia in the bone marrow is helpful in establishing a
diagnosis of destruction thrombocytopenia, but such evi-dence may be absent. Occasional cases of destructivethrombocytopenia show decreased numbers of megakary-ocytes.
It is noteworthy that destruction thrombocytopenias,
like sequestration thrombocytopenia, may be associatedwith hepatosplenomegaly. Hypoproliferative thrombocy-
topenia may be associated with other peripheral cytopenias,
but can only be diagnosed by reduced numbers of
megakaryocytes in marrrow biopsies (histopathology of
core biopsies required). The causes of hypoproliferative
thrombocytopenia are varied and include infectious agents(eg, ehrlichiosis), immune-mediated marrow disease, mar-
row toxicity, marrow aplasia, and myelophthisis.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 39CASE 1
Signalment: Three-year-old female
DSH cat
History: Presented for elective
surgery
HCT 38% WBC 18,600/µl
Hb 12.5 g/dl Neutrophils 8,000/µl
RBC 7.2 x 106/µl Lymphocytes 10,000/µl
TP 6.2 g/dl Eosinophils 300/µlPlatelets Adequate Monocytes 300/µl
Description
Leukogram: There is a leukocytosis characterized by
a marked lymphocytosis. Neutrophil numbers are
within the reference range.
Erythrogram: Red cell parameters and plasma pro-
tein are in the reference range.
Thrombogram: Unremarkable.Interpretation
The principal hematologic alteration is leukocytosis
characterized by lymphocytosis.
Lymphocytosis in cats can be associated with several
conditions such as lymphocytic leukemia, chronic antigenic
stimulation, or physiologic leukocytosis.
Almost all cases of leukemia are characterized by
marked anemia, but in this patient, red cell mass is normal.
Furthermore, in most cases of lymphocytosis due to lym-
phocytic leukemia, circulating lymphocytes are morphologi-cally abnormal, but no abnormal morphology is noted in
this patient. Therefore, the possibility of lymphocyticleukemia is extremely low.
Chronic antigenic stimulation with lymphocytosis is usu-
ally associated with an inflammatory leukogram, but there isno evidence of inflammation in this cat. Consequently, the
most likely interpretation here is physiologic leukocytosis.
Physiologic leukocytosis results from the effects of
excitement (release of epinephrine) on blood flow; theeffect being increased blood flow.
Under normal conditions, for every leukocyte freely cir-
culating in the blood, there is one leukocyte marginated on
the blood vessel walls. Theoretically, only freely circulating
leukocytes are collected when a blood sample is drawn.However, due to the excitement (ie, epinephrine release)
that is often associated with a blood draw, there isincreased blood flow, which causes movement of marginat-ed leukocytes into the freely circulating blood. This, then,
can result in a doubling of the total leukocyte count.
In cats, the result is physiologic lymphocytosis. In dogs,
physiologic neutrophilia generally results.
Physiologic leukopenia can also be seen in those circum-
stances where blood flow is decreased. Perhaps the best
example is the effect of anesthesia. In this case, the number
of leukocytes in the freely circulating blood is reduced as
more and more cells marginate in the face of decreasedheart rate and decreasing blood flow.Chapter 5: Case Studies

40 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 2
Signalment: One-year-old female
Wirehair Terrier
History: Presented for
ovariohysterectomy
HCT 45% WBC 20,300/µl
Hb 15.0 g/dl Neutrophils 18,000/µl
RBC 6.1 x 106/µl Lymphocytes 1,500/µl
TP 6.5 g/dl Monocytes 500/µlPlatelets Adequate Eosinophils 300/µl
Description
Leukogram: There is a leukocytosis (mild) character-
ized by a mild mature neutrophilia and a low normal
to marginally decreased lymphocyte count.
Erythrogram: No abnormalities noted.
Thrombogram: No abnormalities noted.Interpretation
Only white cell changes are observed. Unfortunately,
these findings are somewhat ambiguous.
The marginal lymphocyte count suggests the possibility
of a stress (glucocorticoid-induced) leukogram. A mild
leukocytosis with mild mature neutrophilia also could be
consistent with stress.
However, a mild mature neutrophilia could be a reflec-
tion of mild inflammation even though no specific indica-
tors of inflammation are present. Repeating the CBC in 8
to 12 hours would be expected to clarify the presence or
absence of inflammation.
Finally, the mild leukocytosis with neutrophilia is consis-
tent with physiologic leukocytosis in the dog. Considering
the history and signalment, stress with physiologic leukocy-
tosis is the best interpretation.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 41CASE 3
Signalment: Eight-year-old Boston
Terrier
History: Polyuria and polydipsia of
several weeks’ duration
HCT 55% WBC 14,500/µl
Hb 18.0 g/dl Neutrophils 13,000/µl RBC 8 x 10
6/µl Lymphocytes 750/µl
TP 6.5 g/dl Monocytes 850/µl NRBC 5/100 WBC Platelets Adequate
Description
Leukogram: There is a normal leukocyte count but
an absolute lymphopenia and marginal neutrophilia.
Erythrogram: There is a polycythemia in the face of
a normal plasma protein (absolute polycythemia).
There is also a marginal inappropriate nucleated red
cell response (increased numbers of NRBC in the
absence of polychromasia).
Thrombogram: Unremarkable.Interpretation
Leukogram data (absolute lymphopenia of between
700/µl and 1500/µl and marginal neutrophilia) are consis-
tent with a glucocorticoid-induced leukogram. There is no
evidence of superimposed inflammation or tissue necrosis.
Absolute polycythemia with a possible inappropriate
nucleated red cell response also is entirely consistent with
high levels of circulating glucocorticoids. Glucocorticoids
are known to have a mildly stimulatory effect on RBC pro-duction. High circulating glucocorticoids also are one of
the recognized causes of mild inappropriate nucleated red
cell responses (5 to 10 NRBC/100 WBC).
Considering the history and signalment (Boston Terriers
are prone to endocrinopathies) in conjunction with hemato-
logic findings, Cushing’s disease, either spontaneous or
iatrogenic, should be investigated further.

42 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 4
Signalment: Six-year-old intact female
Poodle
History: Recent onset emesis,
anorexia, polydipsia, and
polyuria
HCT 30% WBC 24,900/µl
Hb 10.0 g/dl Bands 3,000/µlRBC 4.7 x 10
6/µl Neutrophils 18,000/µl
TP 6.5 g/dl Lymphocytes 900/µlPlatelets Adequate Monocytes 3,000/µl
Morphology: Foamy, basophilic cytoplasm in bands,
occasional Döhle bodies.
Description
Leukogram: There is a leukocytosis characterized by
a neutrophilia with a left shift, a lymphopenia, and a
monocytosis. Morphologic abnormalities in neu-
trophils also are noted on the blood film.Erythrogram: Red cell data indicate a mild anemia
characterized by an absence of polychromasia.
Computed MCV (HCT/red cell count in millions x
10) and MCHC (Hb/HCT x 100) are within the
reference range for dogs.Thrombogram: Unremarkable.Interpretation
1.)Inflammatory leukogram with systemic toxemia.
Indicators of inflammation are both the left shift and the
monocytosis. Monocytosis is also an indication of tissue
necrosis. Cytoplasmic basophilia and Döhle bodies in neu-
trophils result from cytoplasmic maturation arrests in devel-
oping stages in the marrow; this is indicative of circulating
toxins in the blood which interfere with differentiation of
granulocyte precursors (systemic toxemia). Systemic tox-
emia can occur as a result of tissue necrosis and toxic disor-
ders (eg, lead poisoning) but in dogs and cats is most com-
monly associated with severe bacterial infections.
2.)Superimposed stress. The lymphocyte count of
between 700/ml and 1500/ml (absolute lymphopenia) is
indicative of stress. The combination of stress and inflam-mation with a left shift is most consistent with active oracute inflammation.
3.)Non-regenerative anemia. Normocytic, nor-
mochromic anemia in the absence of polychromasia is anon-regenerative anemia. The degree of anemia is moder-ate. Considering the presence of a significant inflammatory
leukogram, at least part of the anemia is likely due toinflammatory disease. However, the degree of anemia is
more severe than usually associated with inflammation
Fig. 1 Band cell with slight toxicity (left). Note the foamy, granular, slightly
basophilic cytoplasm. A normal monocyte (right).

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 43alone, which rarely reduces hematocrits in dogs to
less than 35%. Other contributing factors, such as
superimposed blood loss, must also be considered.
4.)Normal platelet count. The normal platelet
count is a significant finding in this case. It is an
encouraging finding in the face of the rather markedinflammation with evidence of systemic toxemia. Aconcern in severe inflammatory conditions is dis-
seminated intravascular coagulation (DIC); the nor-mal platelet count suggests that DIC is not current-ly a problem.
Summary
Overall, hematologic findings suggest a severe
acute inflammatory condition with superimposed
stress, tissue necrosis systemic toxemia, and the
anemia of inflammatory disease. Bacterial infection
is suspected. The absence of thrombocytopenia sug-
gests that despite the seriousness of the condition,
DIC is not present.
The actual diagnosis in the case was E. coli
pyometra.
Fig. 3 A toxic band (left), and a toxic metamyelocyte (right). The cytoplasm of both
cells is too blue.
Fig. 4 A toxic neutrophil with foamy, basophilic cytoplasm
and Döhle bodies.
Fig. 2 Two band cells and a mature neutrophil.

44 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 5
Signalment: Four-year-old intact
female Irish Setter
History: Weight loss and distended
abdomen
HCT 25% WBC 17,500/µl
Hb 8.0 g/dl Neutrophils 10,000/µl
RBC 4 x 106/µl Lymphocytes 3,000/µl
TP 8.2 g/dl Monocytes 4,500/µlPlatelets Adequate
Description
Leukogram: Total white cell count is normal.
However, there is a marked monocytosis.
Erythrogram: There is a moderate normocytic
(MCV = 62 fl) normochromic (MCHC = 33%) ane-
mia with no evidence of polychromasia.
Thrombogram: Unremarkable.Interpretation
1.)Inflammatory leukogram. Although the total white
cell count is normal, the marked monocytosis is a clear indi-
cator of inflammation and tissue necrosis. There is no evi-
dence of superimposed stress. When considered in its
entirety, the leukogram indicates chronic inflammation with
the establishment of a new steady state between marrow
production of leukocytes on the one hand and tissue con-sumption of leukocytes on the other.
2.)Non-regenerative anemia. Normocytic, nor-
mochromic anemias without polychromasia are nonregen-
erative. Pathogenesis of the anemia in this patient is proba-bly complex. Certainly the depression of red cell produc-
tion by inflammatory disease is a major contributing factor.
However, the degree of anemia is too severe to be
explained on the basis of inflammation alone. A potential
source of blood loss should also be sought.
3.)Normal platelet numbers. Normal platelet numbers
in the face of chronic inflammation is a positive finding in
that it indicates the absence of DIC.
4.)Hyperproteinemia. Hyperproteinemia reflects hemo-
concentration and/or increased antibody (immunoglobulin)
production. In this patient, given the presence of a chronic
inflammatory leukogram, antigenic stimulation with
increased immunoglobulin production is almost a
certainty. This can be confirmed by noting
increased globulins as compared to albumin in the
serum chemistry data.
Summary
Hematologic findings are most supportive of a
chronic inflammatory process with tissue necrosis,
antigenic stimulation, and the anemia associated
with inflammation. A second factor exacerbatingthe anemia is also suspected since the degree of
anemia is more than inflammatory processes alone
usually cause.
The actual diagnosis in this case was E. coli
pyometra.
Fig. 5 On scanning magnification, a monocytosis is obvious. Four monocytes and
seven neutrophils.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 45CASE 6
Signalment: Five-year-old female
mixed-breed dog
History: Presented in state of near
collapse and extreme
depression
HCT 50% WBC 5,500/µl
Hb 16.1 g/dl Bands 1,100/µlRBC 7.2 x 10
6/µl Neutrophils 2,000/µl
TP 8.5 g/dl Lymphocytes 900/µlPlatelets Reduced Monocytes 1,500/µl
Description
Leukogram: There is a leukopenia characterized by
neutropenia with a left shift, lymphopenia, and a mar-
ginal monocytosis.
Erythrogram: There is polycythemia with hyperpro-
teinemia.Thrombogram: Thrombocytopenia.Interpretation
1.)Overwhelming inflammation. Left shift and monocy-
tosis indicate inflammation with tissue necrosis. The pres-
ence of the left shift in the face of marked neutropenia indi-
cates that marrow production and release of neutrophils is
unable to keep up with tissue demand (overwhelming
inflammation). This is an unfavorable finding in the dog or
cat and suggests an emergency condition. Overwhelming
inflammation is almost always an acute phenomenon.
2.)Stress leukogram. Absolute lymphopenia with lym-
phocyte counts in the range of 700/µl to 1500/µl is mostcommonly associated with high levels of circulating gluco-
corticoids (stress).
3.)Relative polycythemia. The combination of poly-
cythemia and hyperproteinemia suggests relative poly-
cythemia due to dehydration and hemoconcentration.Leukogram data is not affected by hemoconcentration.
However, other tests in the laboratory profile are also
affected by dehydration and can be used to support theinterpretation of relative polycythemia. BUN, creatinine,and electrolytes all will elevate in the face of dehydration. If
the kidneys are working, urine specific gravity will be con-
centrated. Hyperproteinemia in dehydration will be associ-
ated with elevations in both albumin and globulin levels.
(The other cause of hyperproteinemia, antigenic stimula-
tion, is associated with a relatively greater elevation inglobulins than albumin.) In this patient, considering the
inflammatory nature of the disease, antigenicstimulation may also be contributing to the hyper-
proteinemia.
4.)Possible DIC. Thrombocytopenia in the
face of inflammation, particularly severe and over-
whelming inflammation, is suggestive of possible
DIC. This is a potentially life-threatening syn-
drome and should be confirmed by evaluating a
Fig. 6 A reactive lymphocyte with large nucleus, lacy chromatin pattern with
nucleolar whorls, and basophilic cytoplasm.
Continued

complete DIC panel comprised of platelet count,
prothrombin time, activated partial thromboplas-
tin time, activated partial thromboplastin time,fibrinogen levels and fibrin split products. If three
of the five tests in the panel are abnormal, DIC isconsidered to be present.
Summary
Overwhelming inflammation with tissue necro-
sis and superimposed stress; relative polcythemia;
possible DIC. This patient is in an emergency
state requiring immediate attention.
The actual diagnosis in this animal was E. coli
pyometra.
46 Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 7 A reactive lymphocyte with abundant cytoplasm and small azurophilic
granules.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 47When considered in aggregate, Cases 4, 5, and
6 illustrate several principles of hemogram inter-
pretation, in particular leukogram interpretation.
First, these cases clearly illustrate that inflamma-
tory processes can present with high, low, or nor-
mal total white cell counts. In fact, the primary
value of total leukocyte counts in inflammatory
processes is that they provide some indication of
how well the patient is coping with the inflamma-
tion. If the white cell count is elevated, then mar-
row production and release of leukocytes is
exceeding tissue consumption. This is a favorable
finding for the patient, and accordingly, left shifts
with elevated neutrophil counts have been
termed regenerative left shifts. In contrast, low
white cell counts in inflammatory disorders indi-
cate that tissue utilization of leukocytes exceeds
marrow production and release. This is an unfa-
vorable circumstance for the patient, and left
shifts with low leukocyte counts are therefore
termed degenerative left shifts. Cases of inflam-
matory disease where the total leukocyte counts
are normal are usually chronic conditions where
a new steady state has been reached and marrow
production and release of granulocytes has had
time to expand to meet tissue demand. In these
cases, examination of marrow reveals marked
granulocytic hyperplasia with normal to
increased numbers of mature neutrophils, which
accounts for the absence of a peripheral left shift.A second major principle illustrated in cases 4,
5, and 6 is that leukogram data can be used prog-nostically as well as diagnostically. Case 4, anacute pyometra with a classic acute inflammatoryleukogram, is the simplest case with the best
prognosis for complete, uncomplicated recoveryfollowing hysterectomy. Case 5, a chronic
pyometra with chronic inflammatory leukogram,
also has a relatively good prognosis. However,the chronicity of the process suggests that thesurgery itself may be complicated due to markedvascular proliferation. Case 6, an acute pyometrawith overwhelming inflammation and possible
DIC, has the worst prognosis. This case is clearly
an emergency and requires immediate attention.
Finally, these three cases clearly illustrate that
leukogram data cannot be used to differentiateamong bacterial, viral, and toxic diseases (unless
specific etiologic agents are seen on the bloodfilm). Historically, it has been suggested that bac-
terial diseases cause leukocytosis while viral
infections cause leukopenia. However, in thesethree cases, we have seen examples of a singlebacterial agent associated with the full range ofwhite cell response. Toxic and necrotizingprocesses can induce the same variability in
white cell numbers. Leukogram data are used to
differentiate between inflammatory and non-inflammatory processes, not between infectiousand non-infectious processes.Discussion of Cases 4, 5, and 6

48 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 7
Signalment: Fourteen-year-old
neutered male DSH cat
History: Chronic weight loss with
distended abdomen
HCT 30% WBC 43,200/µl
Hb 9.5 g/dl Neutrophils 38,000/µlRBC 5.6 x 10
6/µl Lymphocytes 2,160/µl
TP 10.0 g/dl Monocytes 2,360/µlPlatelets Adequate Eosinophils 680/µl
Description
Leukogram: There is leukocytosis characterized by
mature neutrophilia and monocytosis.
Erythrogram: There is marginal to no anemia but a
marked hyperproteinemia is present.
Thrombogram: Unremarkable.Interpretation
1.)Chronic inflammatory leukogram. The monocytosis
is a clear indicator of inflammation and tissue necrosis.The marked mature neutrophilia with no left shift suggeststhat the granulocytic compartment of the marrow is signifi-
cantly expanded, a feature of chronicity. Chronicity is alsosuggested by the absence of lymphopenia.
2.)Suspected hypergammaglobulnemia.
Hyperproteinemia is either the result of dehydration or
hypergammaglobulinemia. In this patient, given the
marked inflammatory leukogram, the most likely interpre-tation is hypergammaglobulinemia. Some contribution
from dehydration cannot be absolutely ruled out, but the
degree of hyperproteinemia is too great to be explained bydehydration alone.
Summary
Hemogram data, when considered in conjunction with
the clinical presentation and history, are consistent with a
diagnosis of FIP. FIP was confirmed both serologically
and at necropsy.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 49
Fig. 9 High magnification. A giant toxic band cell (center). Note the blue
cytoplasm (Wright’s stain x 100).CASE 8
Signalment: Three-year-old female
Birman cat
History: Anorexia and dyspnea of
several days’ duration
HCT 25% WBC 54,000/µl
Hb 8.1 g/dl Bands 6,000/µlRBC 5.6 x 10
6/µl Neutrophils 44,000/µl
TP 7.5 g/dl Lymphocytes 1,200/µlPlatelets Reduced Monocytes 2,000/µl
Eosinophils 800/µl
Morphology: There is marked toxicity of neu-
trophils. Occasional reactive lymphocytes are seen.
Description
Leukogram: Marked leukocytosis characterized
by neutrophilia with a left shift, marginal lym-
phopenia and monocytosis.
Erythrogram: There is a mild normocytic nor-
mochromic anemia (MCV = 43 fl, MCHC = 33%).
Thrombogram: Thrombocytopenia.Interpretation
1.)Active inflammatory leukogram with superimposed
stress, tissue necrosis, and systemic toxemia. The left shift
and monocytosis are indicative of inflammation.
Monocytosis also indicates tissue necrosis. High circulating
levels of glucocorticoids (stress) are indicated by the mar-
ginal lymphopenia. Systemic toxemia is indicated by the
presence of toxic neutrophil on the blood film. In this case,
toxicity is severe. In dogs and cats, severe systemic toxemiais most often associated with bacterial infections.
2.) Anemia of inflammatory disease. Mild to moderate
Fig. 8 Low magnification reveals a leukocytosis with neutrophilia and left shift.

normocytic, normochromic non-regenerative ane-
mia is consistent with the anemia of inflammatory
disease.
3.)Possible DIC. Considering the severity of
the inflammation and systemic toxemia, thethrombocytopenia may be an indicator of DIC. A
complete DIC panel is warranted.
Summary
The diagnosis in this patient was bacterial
pyothorax. Based on a positive DIC panel, sub-clinical DIC also was identified.
50
Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 11 A toxic band cell (left), and a toxic neutrophil (right). Again, note the foamy,
basophilic cytoplasm (Wright’s stain x 100).
Fig. 10 Two toxic neutrophils with foamy, basophilic cytoplasm (Wright’s stain x
100).

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 51CASE 9
Signalment: Eight-year-old female
Cocker Spaniel
History: Presented with
generalized
lymphadenopathy
HCT 15% WBC 5,000/µl
Hb 5.0 g/dl Neutrophils 3,000/µl
RBC 2.6 x 106/µl Lymphocytes 700/µl
TP 6.0 g/dl Monocytes 1,000/µlPlatelets Reduced Eosinophils 300/µl
Description
Leukogram: There is leukopenia characterized by
neutropenia and lymphopenia. No white cell morpho-
logic abnormalities are noted on the peripheral blood
film.
Erythrogram: There is marked normocytic nor-
mochromic anemia with no evidence of polychro-
masia.
Thrombogram: Thrombocytopenia.Interpretation
Possible marrow disease. Leukogram, erythrogram, and
thrombogram data, considered collectively, indicate pancy-
topenia. Unexplained cytopenias of one or more marrow
cell line suggests a possible marrow production problem.
Bone marrow examination is required for further evalua-
tion. Possibilities include marrow hypoplasia/aplasia,
myelophthisic syndrome, and myelofibrosis.In this case,
marrow aspirates were highly cellular but abnormal. Few
granulocyte, red cell, and platelet precursors were present.
Instead, the predominant cell seen was a large round cell
with a scant to moderate rim of faintly basophilic cyto-
plasm. The nuclei were round with a lacy reticular patternand very large prominent singular pale blue nucleoli. The
diagnosis was myelophthisic syndrome due to lymphoblas-
tic lymphosarcoma.
Discussion
Case #9 was originally submitted by the referring veteri-
narian as suspect lymphosarcoma; blood was collected in
an attempt to confirm the diagnosis. It should be noted that
where there is generalized lymphadenopathy, the preferred
sample is a lymph node biopsy. Only rarely can a diagnosis
of lymphosarcoma be confirmed with a CBC. In fact, the
most common hematologic finding in cases of lymphosarco-ma is profound non-regenerative anemia, which occurs
when the marrow has been infiltrated by malignant lym-
phoblasts. Lymphopenia and lymphocytosis occur
far less frequently. Lymphopenia results whennormal recirculating lymphocytes become trapped
in massively enlarged lymph nodes and cannot re-
enter the peripheral blood. Lymphocytosis only
Fig. 12 Aspirate of a normal lymph node. Normal small lymphocytes predominate
with several larger prolymphocytes.Continued

occurs when the marrow is so infiltrated that
malignant cells spill over in high numbers into the
peripheral blood. Lymphocytosis with malignant
cells in circulation is, therefore, a late finding in
most cases of lymphosarcoma even though it is
the only circumstance where the diagnosis can be
confirmed with the CBC alone.
52 Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 13 Aspirate of a lymph node with lymphoma. The majority of the cells are large
blasts with very large nuclei and prominent nucleoli.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 53
Fig. 14 Low magnification of pleural fluid. Normal small lymphocytes predominate.
Red cells are seen in the background. This is typical of a chylous effusion.CASE 10
Signalment: Six-year-old female DSH
cat
History: Sudden onset dyspnea of
approximately 2 days’
duration
HCT 45% WBC 10,600/µl
Hb 15.0 g/dl Neutrophils 10,000/µlRBC 9.0 x 10
6/µl Lymphocytes 200/µl
TP 4.1 g/dl Eosinophils 400/µlPlatelets Adequate
Description
Leukogram: The only abnormality noted in the
leukogram is profound lymphopenia.
Erythrogram: Red cell parameters fall within the ref-
erence range. However, hypoproteinemia is present.
Thrombogram: No abnormalities noted.Interpretation
1.)Profound lymphopenia. The most common cause of
lymphopenia is high circulating glucocorticoid levels (stress
leukogram). However, elevated glucocorticoids generally
cause lymphopenias in the range of 700/µl to 1500/µl.
When lymphocyte counts drop below 700/µl, other cases of
lymphopenia should be considered. Profound lymphopenias
can be caused by anything that interrupts the normal circu-latory pattern of lymphocytes. Lymphocytes are predomi-
nantly long-lived cells, which circulate in peripheral blood
to lymph nodes, migrate through the lymph nodes and
enter the efferent lymphatics, and travel via lymph to re-enter the blood via the thoracic duct. Causes of profound
lymphopenias are therefore primarily lymphatic obstruction
(neoplasias), and lymphatic rupture (chylothorax, chy-
loperitoneum). With the history of sudden onset dyspnea,
chylothorax should be strongly considered in this patient.
2.)Hypoproteinemia. Hypoproteinemia can result from
loss of blood or lymph, protein losing enteropathy, protein-
Continued

54 Nestlé PURINA Hemogram Interpretation for Dogs and Catslosing nephropathy or lack of protein production
by a damaged liver. In this case, the combination
of profound lymphopenia, hypoproteinemia, and
clinical dyspnea all indicate an underlying chylous
effusion.
Summary
The diagnosis of chylous effusion (chylotho-
rax) was confirmed cytologically by evaluation of
excessive pleural fluid.
Fig. 15 High magnification of Fig. 14. Normal small lymphocytes.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 55CASE 11
Signalment: Eight-week-old male
Beagle
History: Sudden onset of
respiratory distress and
diarrhea (dark feces) of
2 days’ duration
HCT 25% WBC 19,100/µl
Hb 8.1 g/dl Bands 1,100/µlRBC 4.0 x 10
6/µl Neutrophils 14,000/µl
TP 4.5 g/dl Lymphocytes 1,000/µlPlatelets Normal Eosinophils 3,000/µl
numbers,
some large
Morphology: Mild to moderate polychromasia
Description
Leukogram: There is a leukocytosis (mild) with a
mild neutrophilia and left shift, eosinophilia, and lym-
phopenia.
Erythrogram: There is a moderate anemia with mild
to moderate polychromasia. There is mild to moder-
ate hypoproteinemia.
Thrombogram: Unremarkable.Interpretation
1.)Acute inflammatory leukogram with systemic hyper-
sensitivity and superimposed stress. Indicators of inflamma-
tion are the left shift and eosinophilia. The eosinophilia also
is an indicator of systemic hypersensitivity. Considering theage of the patient, the possibility of circulating larvae ofintestinal parasites (hookworms, ascarids) as a cause of thehypersensitivity should be investigated. An associated
regenerative anemia suggesting blood loss would be sup-
portive evidence of parasitemia. Even in the absence of
hookworm ova in the feces, late stage larvae in the gut arecapable of causing blood loss before ova are produced. The
marginal lymphopenia in this patient is best interpreted as
indicative of high circulating levels of glucocorticoids
(stress).
2.)Regenerative anemia. A mild to moderate anemia
accompanied by mild to moderate polychromasia is sugges-
tive of a regenerative anemia. An absolute reticulocytecount would probably be useful in confirming this interpre-tation. Regenerative anemias are the result of either bloodloss or hemolysis. Considering the suspicion of intestinal
parasitism and the findings on the leukogram, blood loss
anemia is the most likely cause.
3.)Hypoproteinemia. Young dogs (less than 9 months to 1
year) generally have lower total protein levels than adultshave (in the range of 5.0 g/dl to 6.0 g/dl) but the level here is
quite low and is a clear hypoproteinemia. Hypoproteinemia
can result from loss of blood or lymph, protein los-ing nephropathy (confirmed by protein loss inurine), protein losing enteropathy (associated with
diarrhea with voluminous stools), or lack of protein
(albumin) production by the liver (confirmed by
other evidence of liver pathology). In this case thelikely cause is blood loss as a result of intestinalparasitism.
Summary
Considered collectively, hematologic data sug-
gests severe hookworm infection with associatedblood loss anemia and hypoproteinemia.
Leukogram data suggests that there are still sys-
temically migrating larvae on their way to the
gut causing a hypersensitivity reaction and
inflammation.
Fig. 16 Two normal eosinophils.

56 Nestlé PURINA Hemogram Interpretation for Dogs and CatsInterpretation
1.)Inflammatory leukogram with tissue necrosis and sys-
temic hypersensitivity. Monocytosis and eosinophilia are
clear indicators of inflammation even though total white cell
count is in the reference range. Furthermore, monocytosis
suggests demand for phagocytosis (tissue necrosis) while
eosinophilia (persistent) signals a systemic hypersensitivity
reaction. Considering that total leukocyte count is normal,
there is no left shift, and there is no lymphopenia, the
inflammation is most likely chronic. Hyperproteinemia due
to hypergammaglobulinemia and the mild to moderate non-
regenerative anemia of inflammation might be anticipated.
2.)Severe nonregenerative anemia with inappropriate
nucleated red cell response. Mild to moderate polychroma-
sia in the face of severe anemia is an inadequate response.
Furthermore, the number of nucleated red cells present isfar too high for the degree of polychromasia and theresponse is therefore classified as inappropriate. The nota-
tion of mitotic red cell precursors in the peripheral blood is
also quite disturbing and suggests that some circulating
nucleated red cells are fairly immature (rubricytes or more
primitive). Inappropriate nucleated red cell responses are
the result of marrow stromal damage (heavy metal toxicity,
anoxia, high circulating glucocorticoids), inadequate
splenic function, fractures, extramedullary hematopoiesis,or red cell marrow exhaustion. Compared to adult animals,very young animals have less marrow reserve. Considering
the severity of anemia in this patient, the inappropriatenucleated response here probably results from marrow
stromal damage in the form of anoxic injury and red cell marrowexhaustion as the red cell compartment attempts to respond to the
severe anemia. This is an unfavorable finding in this puppy.
Summary
This puppy is a littermate of the puppy in Case 11, seen one week
later, also untreated at the time of presentation. This puppy, like thepuppy in the previous case, has severe hookworm infestation.Migrating larvae are still probably present (based on the leukogram)
as are parasitic forms in the bowel. With the inability of the red cell
marrow to keep pace with the loss of blood, the prognosis is guarded.
Note that the inflammatory leukogram in this puppy, seen seven days
after the first, is chronic and that there is no evidence of a stress leuko-gram (even though the puppy is undoubtedly “stressed”) which sug-
gests chronic antigenic stimulation.CASE 12
Signalment: Nine-week-old female
Beagle
History: Diarrhea and listlessness
of several weeks’ duration
HCT 15% WBC 17,000/µlHb 5.6 g/dl Neutrophils 10,000/µl
RBC 2.7 x 10
6/µl Lymphocytes 2,000/µl
TP 4.5 g/dl Monocytes 2,500/µlNRBC 30/100 WBC Eosinophils 2,500/µlPlatelets Adequate
Morphology: Mild to moderate polychromasia, many
NRBC, some mitotic.
Description
Leukogram: There is a normal leukocyte count char-
acterized by a marked eosinophilia and monocytosis.
Erythrogram: There is a marked anemia with an
inappropriate nucleated red cell response (too many
nucleated RBCs relative to the degree of polychroma-
sia). There is also moderate hypoproteinemia.
Thrombogram: Unremarkable.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 57CASE 13
Signalment: Fourteen-week-old male
Beagle
History: Listless, anorectic, pale
mucous membranes
HCT 12% WBC 10,000/µl
Hb 3.0 g/dl Neutrophils 7,000/µl
RBC 2.3 x 106/µl Lymphocytes 1,000/µl
TP 3.8 g/dl Monocytes 1,500/µlPlatelets Increased Eosinophils 500/µl
numbers
with many large platelets
Morphology: Moderate anisocytosis and poikilocyto-
sis with moderate numbers of red cell fragments.
Numerous cells have large pale centers.
Description
Leukogram: Total white cell count is within normal
limits, but there is a lymphopenia (marginal) and mild
monocytosis.
Erythrogram: There is a marked microcytic
hypochromic anemia (MCV = 12/2.3 x 10 = 52 fl,
MCHC = 3/12 x 100 = 25%). Hypochromia and
microcytosis are confirmed by red cell morphology
on the blood film. There is also red cell fragmenta-
tion.
Thrombogram: Thrombocythemia.Interpretation
1.)Inflammatory leukogram with superimposed stress
and tissue necrosis. Monocytosis indicates inflammation
and tissue necrosis. Marginal lymphopenia indicates super-
imposed stress. It is difficult to ascertain whether the
process is acute or chronic. Repeat leukograms might behelpful in this regard.
2.)Iron-deficiency anemia. Marked microcytic
hypochromic anemia is highly suggestive of chronic blood
loss with resultant iron deficiency. Iron is required for
hemoglobin formation. In turn, red cell hemoglobinization
regulates division of red cell precursors in the marrow.When iron is unavailable for adequate hemoglobin synthe-sis, precursors undergo additional divisions in the marrow,
becoming smaller and smaller. Red cells eventually
released into peripheral blood are both smal (microcytic)
and deficient in hemoglobin (hypochromic). Although the
mechanism is not clearly understood, hypochromic red cells
are also more fragile than normal, hence the increased
numbers of red cell fragments on the blood film.
3.)Reactive thrombocythemia. With the severity of the
anemia, it is likely that circulating levels of the red cell
growth factor erythropoietin are quite high. Erythropoietin
stimulates both red cell production and platelet produc-
tion. The thrombocythemia with megaplatelets (immature
platelets) is therefore most likely a reactive thrombo-
Fig. 17 Scanning magnification. Note the large unstained areas of central pallor in
the red cells.Continued

cythemia in response to the erythropoietin. The
anemia is non-regenerative (note minimal poly-
chromasia) because the iron-deficient marrow is
unable to respond. White cell production is notaffected by erythropoietin.
Summary
This pup is from the same litter as Cases 11
and 12. Like the others, it was untreated at the
time of presentation. The primary diagnosis is
severe hookworm infestation with iron deficiency
anemia resulting from chronic blood loss.
58 Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 18 High magnification. The marked central pallor of the red cells typical of iron
deficiency is easily apparent. A red cell fragment (schizocyte) is at left center.
Fig. 19 High magnification. A schizocyte is at center. Several polychromatophils are
also present.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 59CASE 14
Signalment: One-year-old male Siamese
cat
History: Sudden onset depression
and anorexia with pale,
icteric mucous membranes
HCT 20% WBC 18,700/l
Hb 6.4 g/dl Bands 1,000/lRBC 3.7 x 10
6/l Neutrophils 15,000/l
TP 6.5 g/dl Lymphocytes 1,200/lPlatelets Adequate Monocytes 1,500/l
Morphology: Minimal polychromasia is present.
Numerous RBCs contain chains of small basophilic
bodies or ring forms.
Description
Leukogram: There is mild leukocytosis with neutrophil-
ia, left shift, monocytosis, and a marginal lymphopenia.
Erythrogram: There is a moderate normocytic nor-
mochromic anemia. (MCV = 54 fl, MCHC = 32%).
The basophilic bodies on the red cells are consis-
tent with Hemobartonella felis.
Thrombogram: Unremarkable.Interpretation
1.)Active inflammatory leukogram with tissue necrosis
and superimposed stress. Indicators of inflamation are the
left shift and the monocytosis. Monocytosis is also an indi-
cator of tissue necrosis. The marginal lymphopenia is
indicative of superimposed stress.
2.)Anemia due to hemobartonellosis. The presence of
large numbers of Hemobartonella bodies on the blood film
establishes the diagnosis of hemobartonellosis. In its pri-
mary form, hemobartonellosis is a regenerative hemolytic
anemia. In this case, there is no evidence of regeneration
(no polychromasia) at the time of presentation.Hemobartonellosis may also be seen as a non-regenerative
anemia when it occurs secondarily to serious immunosup-
pressive disorders such as FeLV, FIV, or FIP. Primary
hemobartonellosis responds well to antibiotic therapy;
however, when hemobartonellosis occurs secondarily, theprognosis is guarded. Clearly, this patient should be moni-
tored over the next few days for the appearance of poly-
chromasia and reticulocytosis. Tests for FeLV, FIV, andFIP are warranted. The inflammatory leukogram in this
case is probably in response to the destruction of infected
Fig. 20-22 Numerous red cells parasitized by Hemobartonella felis are seen in the
three figures. Organisms are present singly and in chains. (Wright’s stain
x 100).Continued

red blood cells by tissue macrophages. Red cell
destruction is a form of tissue necrosis.
Summary
Polychromasia/reticulocytosis became promi-
nent within 24 to 48 hours after initial presenta-
tion. Over the same period, the number of cells
containing Hemobartonella bodies dropped dramat-
ically as infected cells were removed from the
blood. Tests for FeLV, FIV, and FIP were nega-
tive. The anemia responded favorably to tetracy-
cline therapy. Clearly, this was a case of primary
hemobartonellosis, which presented in the first
few days of infection before a fully developed
regenerative response was apparent.
60 Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 21
Fig. 22

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 61CASE 15
Signalment: Five-year-old female Basset
Hound
History: Sudden onset lethargy,
emesis, anorexia, and yellow
mucous membranes of
approximately 4 days’duration
HCT 25% WBC 19,500/µl
Hb 7.0 g/dl Bands 2,000/µlRBC 3.0 x 10
6/µl Neutrophils 15,000/µl
TP 7.0 g/dl Lymphocytes 1,200/µlPlatelet Adequate Monocytes 1,300/µl
Morphology: Moderate to marked polychromasia,
numerous schizocytes, and spherocytes.
Description
Leukogram: There is a mild leukocytosis with neu-
trophilia, left shift, marginal monocytosis, and mar-
ginal lymphopenia.Erythrogram: There was moderate anemia charac-
terized by polychromasia, schizocytes and sphero-
cytosis.Thrombogram: Unremarkable.Interpretation
1.)Inflammatory leukogram with tissue necrosis and
superimposed stress. The left shift and marginal monocyto-
sis are indicators of inflammation. Marginal monocytosis
also indicates tissue necrosis. The marginal lymphopenia
strongly suggests superimposed stress.
2.)Suspected immune-mediated hemolytic anemia.
Anemia with moderate to marked polychromasia implies a
regenerative anemia. Regenerative anemias are either the
result of hemolysis or blood loss. In this case, the presence
of spherocytes on the peripheral blood film strongly sug-
gests an immune-mediated hemolytic process. A direct
antiglobulin test (Coomb’s test, DAT) could be run for con-
firmation.
Comment
Immune-mediated hemolytic anemias are often accompa-
nied by inflammatory leukograms with tissue necrosis. The
source of the tissue necrosis is the breakdown of red bloodcells both in the circulation and in tissues rich in
Continued
Fig. 23 Scanning magnification. Red cells exhibit anisocytosis. Several
polychromatophils and nucleated red cells are present. Leukocytes include
two monocytes (at center), several mature neutrophils, and a band cell (top
left center).

macrophages such as spleen. The adequate
platelet count is a favorable finding in this patient;
some cases of immune-mediated hemolysis arealso accompanied by immune-mediated thrombo-cytopenia. Patients with both hemolysis andthrombocytopenia are generally less responsive to
therapy than immune-mediated hemolysis alone.
62
Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 24-25 High magnification. Note the presence of spherocytes, several
polychromatophils and a nucleated red (Fig. 5.25). Red cell changes are
consistent with immune-mediated hemolytic anemia. White cells present
include a monocyte (Fig. 5.25), a band cell (Fig. 5.25), and mature
neutrophils. The neutrophil in Fig. 5.25 is slightly toxic.
Fig. 25

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 63CASE 16
Signalment: Eight-year-old female
German Shepherd
History: Chronic wasting syndrome
HCT 30% WBC 15,350/µl
Hb 9.0 g/dl Neutrophils 8,000/µl
RBC 4.0 x 106/µl Lymphocytes 3,000/µl
TP 6.5 g/dl Monocytes 4,000/µlPlatelets Adequate Eosinophils 350/µl
Reticulocyte count = 5 %
Description
Leukogram: There is a marked monocytosis; all other
values are within the reference range.
Erythrogram: There is a mild marginally macrocytic
(calculated MCV = 75 fl) marginally hypochromic (cal-
culated MCHC = 30%) anemia with an absolute reticu-
locyte count of approximately 200,000/µl (reference
range to 80,000/µl). Spiculated poikilocytosis is promi-
nent.
Thrombogram: Unremarkable.Interpretation
1.)Chronic inflammatory leukogram with tissue necro-
sis. Monocytosis is an indicator of both inflammation and
tissue necrosis. The normal total leukocyte count, absence
of a neutrophilia and left shift, and absence of lymphope-
nia, all suggest the establishment of a new white cell steady
state with marrow production of leukocytes balancing tis-
sue demand (utilization). There is probably granulocytic
hyperplasia in the marrow and shortened circulating half-
life of granulocytes in the peripheral blood. These are clas-
sic features of chronic inflammation.With the presence of a
chronic inflammatory leukogram, several other hemogram
changes might be anticipated. The mild to moderate non-regenerative anemia associated with inflammatory disease
is to be expected. Furthermore, chronic inflammation is
often associated with hyperproteinemia as a result of hyper-
gammaglobulinemia.
2.)Regenerative acanthocytic anemia. Anemia with
polychromasia and reticulocytosis is regenerative.
Consequently, the anemia in this case cannot be explained
as the anemia of inflammatory disease alone. Regenerative
anemias result from either blood loss or hemolysis.
Acanthocytes are red cells with 2 to 10 blunt, glove-likeprojections from the surface. Acanthocytic anemia in dogshas been associated with liver disease. In particular, acan-
thocytic regenerative anemia hase been associated with
Fig. 26 Scanning magnification. Monocytosis is apparent. Red cells exhibit
anisocytosis and polychromasia.Continued

bleeding hemangiosarcomas of the liver, especially
in middle-aged, large breed dogs such as the
German Shepherd patient in this case. A possibili-
ty of abdominal hemangiosarcoma should there-
fore be strongly considered here. The finding of
adequate platelets is significant and favorable.
Many cases of abdominal hemangiosarcomas pre-sent either with disseminated or localized coagu-
lopathies; these are generally thrombocytopenic.
Summary
Radiography revealed an enlarged spleen and
liver. At exploratory laparotomy, multiple neoplas-
tic nodules were found in both organs.
Histopathology confirmed the preliminary diagno-sis of hemangiosarcoma. Many of the nodulesappeared to have necrotic centers; tumor necrosiswas the presumed cause of the inflammatoryleukogram.
64
Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 27 High magnification. Two polychromatophils and nucleated red cells (left).
Numerous red cells have multiple finger-like projections (acanthocytes).
Platelets are obvious.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 65CASE 17
Signalment: Fifteen-year-old neutered
female DSH cat
History: Weight loss, pica, and
hyperexcitability
HCT 35% WBC 11,000/µl
Hb 12.0 g/dl Neutrophils 8,500/µlRBC 7.5 x 10
6/µl Lymphocytes 1,700/µl
TP 6.5 g/dl Monocytes 500/µlPlatelets Adequate Eosinophils 300/µl
Morphology: 50% or more of the red cells contain
discernible Heinz bodies.
Description
Leukogram: Unremarkable
Erythrogram: Numerical data are unremarkable;
however, the presence of large numbers of Heinz
bodies on the blood film is noteworthy.
Thrombogram: Unremarkable.Interpretation
Possible metabolic disease. In cats, the presence of large
numbers of Heinz bodies in the absence of hemolytic ane-
mia has been associated with metabolic and endocrinologic
diseases. The most frequent associations have been with
diabetes mellitus, hyperthyroidism, and liver disease.
Summary
Further evaluation of this patient led to a diagnosis of
hyperthyroidism. As is common in these cases, a routine
clinical chemistry panel revealed no abnormalities. The
diagnosis was confirmed based upon markedly elevated
resting T4levels.
Fig. 29 With vital stains, Heinz bodies are much more
obvious. In this new methylene blue-stained
preparation, they are seen as blue precipitates within
the red cell (100x).
Fig. 28 Several prominent Heinz bodies (seen as nose-like projections from the red
cell surface). Note the lack of polychromasia (Wright’s stain x 100).

66 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 18
Signalment: Ten-year-old female
mixed-breed dog
History: Polyuria and polydipsia of
3 months’ duration with
progressive anorexia
HCT 24% WBC 8,500/µl
Hb 7.8 g/dl Neutrophils 7,000/µlRBC 3.8 x 10
6/µl Lymphocytes 1,000/µl
TP 3.2 g/dl Monocytes 500/µlPlatelets Adequate
Morphology: Numerous Burr cells seen
Description
Leukogram: The principal abnormality noted is
marginal lymphopenia.
Erythrogram: There is a moderate normocytic
(MCV = 63 fl), normochromic (MCHC = 32%)
anemia with Burr cells. No polychromasia is
noted.Thrombogram: Unremarkable.Interpretation
1.)Stress leukogram. Marginal lymphopenia strongly
suggests high circulating glucocorticoid levels and a stress
leukogram.
2.)Non-regenerative anemia with Burr cells. The
absence of polychromasia confirms nonregenerative ane-mia in this patient. Red cell indices within the reference
range are expected. Burr cells are elongated (oval) RBCswith ruffled membranes. In humans, spiculated RBCs with
Burr cell morphology have often been associated withrenal disease. This association is less clear in animals.
However, large numbers of spiculated red cells (acantho-
cytes, Burr cells) in canine blood films have been associat-
ed with either liver disease or renal disease. In general,
when acanthocytes are predominant, liver disease is more
Fig. 30 Scanning magnification. Poikilocytosis (variable red cell shape) is striking.
Numerous elongated red cells (ovalocytes).

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 67likely; when Burr cells are prevalent, renal disease should
be higher on the differential. Renal disease is also fairly
consistently associated with non-regenerative anemia with-
out red cell morphologic changes. Considering the clinical
signs, the anemia, and the Burr cells, the possibility of renal
disease should be thoroughly investigated in this patient.
Summary
Clinical chemistry and urinalysis confirmed the diagno-
sis of renal failure (BUN = 242, creatinine = 4.3, urine spe-
cific gravity = 1.009). Renal biopsy established a morpho-
logic diagnosis of end-stage kidney disease (nephrosclero-
sis). It is of interest that minimal inflammation was seen
histologically; this is consistent with the lack of an inflam-matory leukogram.
Fig. 31 High magnification. Elongated red cells with ruffled membranes (Burr cells)
have been associated with metabolic disorders, particularly renal disease,
in humans and dogs.

68 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 19
Signalment: Five-year-old female
Coonhound
History: Gradually worsening CNS
signs – dullness, rare
seizures, occasional circling
HCT 35% WBC (corrected) 15,500/µl
Hb 11.1 g/dl Neutrophils 10,000/µl
RBC 5.2 x 106/µl Lymphocytes 3,000/µl
TP 6.5 g/dl Monocytes 2,500/µlNRBC 85/100 WBC Platelet Adequate
Morphology: No polychromasia seen
Description
Leukogram: Total white cell count is within the refer-
ence range; however, there is a marked monocytosis.
Erythrogram: There is a mild anemia with no
increase in polychromasia and pronounced inappro-
priate nucleated red cell response (increased nucle-ated red cells in the absence of significant polychro-masia).
Thrombogram: Unremarkable.Interpretation
1.)Chronic inflammatory leukogram with tissue necro-
sis. Monocytosis indicates both inflammation and tissue
necrosis. The normal white cell count, absence of a leftshift, lack of lymphopenia, and the monocytosis are consis-
tent with chronic inflammation.
2.)Bone marrow stromal damage. An inappropriate
nucleated red cell response is usually associated with dam-
age to bone marrow stroma and indiscriminate leakage of
immature red cells into circulation. Causes include endo-
toxemia, high circulating levels of glucocorticoids, frac-
tures, lead poisoning (in dogs), and FeLV disease in cats.
Other causes of inappropriately increased numbers of
nucleated red cells in circulation include extramedullary
hematopoiesis and splenic dysfunction or splenectomy. The
degree of inappropriate response is of interpretive signifi-cance. Nucleated red cell counts of greater than 10/100
WBC are marked and are most likely the result of lead poi-
soning in the dog, while in the cat, they most commonly areassociated with FeLV-induced marrow disease. In the pre-
sent case, lead poisoning is the most likely diagnosis. Lead
Fig. 32 Scanning magnification. Numerous nucleated cells, many of them nucleated
red cells, are seen. There also appears to be a left shift.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 69poisoning can also cause tissue necrosis with mono-
cytosis and CNS clinical signs as seen here.
Summary
Blood lead levels of 0.7 ppm confirmed the sus-
pected diagnosis of lead poisoning.
Comment
Basophilic stippling of RBCs has long been cited
as an important hematologic finding in cases of lead
poisoning. However, basophilic stippling is not a
constant finding and was not present here. Blood
films in this case were made from blood collected
with EDTA; basophilic stippling is more easily
demonstrated in films made from blood not treated
with anticoagulants. When lead poisoning is sus-
pected, it may be useful to prepare several direct
blood films for staining and evaluation.
Fig. 33 High magnification. The number of nucleated red cells is too high for the
degree of polychromasia (inappropriate nucleated red cell response). Note
that the NRBC (center) is stippled (contains basophilic cytoplasmic
precipitates). The two neutrophilic bands (left) have toxic cytoplasm.
Fig. 34 High magnification. The nucleated red cell (left) is quite immature.
Fig. 35 High magnification. Three nucleated red cells and a toxic metamyelocyte.

70 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 20
Signalment: Seven-year-old male DSH cat
History: Chronic weight loss and
anorexia. At presentation, the
cat is cachectic, weak, and
depressed, with pale mucous
membranes.
HCT 12% Neutrophils 1,000/µl
Hb 4.0 g/dl Lymphocytes 500/µlRBC 2.6 x 10
6/µl Monocytes 300/µl
TP 6.0 g/dl Eosinophils 200/µl NRBC 400/100 WBC Nucleated cells 30,000/µl
Platelets Reduced
(6,000/µl
corrected)
Blasts & unclassifed 4,000/µl
Morphology: Very high nucleated red cell count with
recognizable red cell precursors in all stages of differ-
entiation. Remaining nucleated cells are largely blasts
and unclassified cells. Blasts appear to be of both red
cell and granulocytic lines.
Description
Leukogram: Leukopenia with marked neutropenia,
lymphopenia, and increased numbers of blasts and
unclassified cells.Erythrogram: Severe normocytic, normochromic
anemia with profound metarubricytosis.
Thrombogram: Thrombocytopenia.Interpretation
1.)Pancytopenia. Mature forms of all cell lines (white
cell, red cell, and platelet) are present in markedly reduced
numbers. This finding alone suggests marrow disease and
would warrant marrow evaluation. In the cat, the primary
concerns with a history of chronic disease are FeLV or FIPinfection.
2.)Inappropriate nucleated red cell response.
Metarubricytosis in the absence of polychromasia is aninappropriate nucleated red cell response and suggests
marrow stromal disease. In this patient, where numerous
stages of RBC precursors are seen in the blood, it is highly
suggestive of FeLV related marrow disease. Because of themarked metarubricytosis, total nucleated cell count must
be corrected. This is done according to the following for-mula:
Fig. 36 Low magnification shows large numbers of nucleated red cells. Note that
the film is very thin, suggesting severe anemia (Wright’s stain x 50).Total nucleated □
cell count
In this case, 30,000 x□100 + NRBC/100 WBCx
□100
□100 + 400100Corrected □
WBC count
6,000=
=

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 713.)Probable FeLV related erythroleukemia. The
presence of numerous blasts and abnormal unclas-
sifed cells further supports the suggestion of FeLV
related disease with a leukemic phase. Because
blasts and poorly differentiated precursors of both
red cell and granulocyte lineage are seen, ery-
throleukemia (combined red and white cell
leukemia) is the best specific diagnosis.
Comment
The cat tested positive for FeLV and negative
for FIP.
Fig. 38 Various stages of nucleated red cell differentiation (Wright’s stain x 100).
Fig. 37 Three metarubricytes, a lymphocyte, and a nucleated cell that is difficult to
classify (Wright’s stain x 100).

72 Nestlé PURINA Hemogram Interpretation for Dogs and CatsInterpretation
1.)Stress leukogram. Marginal lymphopenia is sugges-
tive of stress.
2.)Consumptive/destructive thrombocytopenia.
Thrombocytopenias can result from a lack of production of
platelets by the marrow, sequestration of platelets in
peripheral tissues (hypersplenism), consumption of
platelets in hypercoagulation syndromes (DIC), or destruc-
tion of platelets by anti-platelet antibodies (immune-mediat-ed thrombocytopenia). Hypersplenism is rare in animals
and is associated with an enlarged spleen, which was notpresent in this case. Production thrombocytopenias are dif-
ferentiated from consumption/destruction thrombocytope-
nias with bone marrow evaluation. Production thrombocy-topenias are characterized by reduced numbers of marrow
megakaryocytes, while consumption/destruction thrombocy-
topenias have normal to increased numbers of megakary-
ocytes. Marrow morphology in this cat strongly suggests a
consumption/destruction problem. Given the absence of an
inflammatory leukogram, DIC and consumption thrombocy-
topenia are highly unlikely. This is, therefore, most likely acase of immune-mediated thrombocytopenia.
3.)Anemia of uncertain origin. The anemia is mild, and,
based on peripheral blood findings, non-regenerative.However, bone marrow morphology indicates red cell
regeneration. Either this is a regenerative anemia (blood
loss or hemolytic) in its earliest stages (before peripheral
reticulocytosis has had time to occur – 72 to 96 hours.), or
an immune-mediated marrow disease directed against late
stage red cell precursors. Repeated CBCs should help clari-fy the situation; if truly regenerative, polychromasia will be
present on blood films within the next few days.
Summary
Blood films taken within 24 hours of presentation contained signifi-
cant numbers of reticulocytes, thus confirming the regenerative nature ofthe anemia. No spherocytes were observed. A presumptive diagnosis ofblood loss anemia secondary to thrombocytopenia was made. Steroid
therapy was initiated to treat the presumed immune-mediated thrombo-cytopenia. A rising platelet count was seen within 24 hours of therapy
induction. Platelet counts had returned to normal by 10 days, confirmingthe diagnosis of immune-mediated thrombocytopenia.CASE 21
Signalment: Four-year-old female Persian cat
History: Sudden onset epistaxis with
numerous petecchiae seen on
physical examination
HCT 30% WBC 11,950/µlHb 10.0 g/dl Neutrophils 10,000/µl
RBC 6.2 x 10
6/µl Lymphocytes 1,100/µl
TP 6.7 g/dl Monocytes 850/µlPlatelets Rare
Bone marrow examination: Very cellular. Erythroid
hyperplasia with left shift and marked megakaryocytic
hyperplasia evident.
Description
Leukogram: All leukocyte values are within the refer-
ence range but lymphocyte numbers are marginally low
(marginal lymphopenia).Erythrogram: There is a mild anemia with no reported
polychromasia. Computed red cell indices are within the
reference range (MCV = 47 fl, MCHC = 33%).Thrombogram: Thrombocytopenia.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 73Interpretation
1.)Overwhelming inflammation with tissue necrosis. The
left shift and monocytosis indicate inflammation.
Monocytosis also indicates tissue necrosis with demand for
phagocytosis. The low total white cell count and neutropenia
suggest an inability of marrow production to keep pace with
tissue demand; hence, the inflammatory process is severe and
overwhelming with a guarded prognosis.
2.)Stress leukogram. Marked lymphopenia indicates
stress. The degree of lymphopenia is so great that other
possible causes of lymphopenia should also be considered.
3.)Non-regenerative anemia. Anemia without polychro-
masia is non-regenerative. The degree of anemia may be
more severe than is indicated by the red cell data because
the animal appears to be dehydrated (elevated plasma pro-
tein in the face of severe diarrhea suggests hemoconcentra-tion from dehydration, other indicators of hemoconcentra-
tion could be found in urinalysis data and chemistry panels,
eg, concentrated urine specific gravity, elevated BUN, crea-tinine, serum albumin, and electrolytes). Considering that
thrombocytopenia is also present and that stools are tarry,the possibility of an early blood loss anemia (before poly-
chromasia becomes evident) should be considered.
4.)Possible DIC. The combination of thrombocytopenia
and schizocytosis on the peripheral blood film suggest the
possibility of disseminated intravascular coagulopathy. A
full DIC panel (prothrombin time, activated partial throm-
boplastin time, fibrin split products, fibrinogen, and
platelet count) should be run. If three of the five tests areabnormal, DIC is confirmed. Overwhelming inflammatorydisease is frequently associated with secondary DIC.
Summary
The final diagnosis in this patient is parvoviral enteritis
with secondary bacterial enteritis, endotoxemia and DIC. Fibrin split
products were elevated, PT and PTT were prolonged, and platelet count
was reduced. Blood loss through the intestinal tract was the cause of theanemia. Within 24 hours of presentation, polychromasia became apparent
on peripheral films.CASE 22
Signalment: One-year-old male Cocker
Spaniel
History: Severe depression and
severe, acute diarrhea with
dark tarry stools
HCT 33% WBC 6,000/µlHb 11.0 g/dl Bands 1,000/µlRBC 5.0 x 10
6/µl Neutrophils 1,500/µl
TP 8.0 g/dl Lymphocytes 500/µlPlatelets Rare Monocytes 3,000/µl
Morphology: Neutrophils and bands are foamy and
basophilic. Moderate poikilocytosis characterized pri-
marily by schizocytes.
Description
Leukogram: There is a leukopenia characterized by a
marked neutropenia with a left shift (degenerative left
shift), a profound lymphopenia, and a marked mono-
cytosis.Erythrogram: There is a mild anemia with poikilocy-
tosis characterized primarily as schizocytosis. There is
hyperproteinemia. There is no polychromasia.
Thrombogram: Marked thrombocytopenia.

74 Nestlé PURINA Hemogram Interpretation for Dogs and CatsCASE 23
Signalment: Two-year-old male DSH cat
History: Weight loss, anorexia, and
recent diarrhea
HCT 35% WBC 2,200/µl
Hb 11.7 g/dl Neutrophils 500/µl
RBC 6.2 x 106/µl Lymphocytes 700/µl
TP 7.0 g/dl Monocytes 1,000/µlPlatelets Reduced
Morphology: Neutrophils seen are extremely toxic.
Description
Leukogram: There is a marked leukopenia character-
ized by a marked neutropenia and lymphopenia and
systemic toxemia.Erythrogram: There is a minimal to mild anemia in the
absence of polychromasia.Thrombogram: Thrombocytopenia.Interpretation
1.)Possible marrow disease with systemic toxemia.
There are no absolute indicators of inflammation in the
leukogram and concomitant thrombocytopenia suggests a
possible marrow production problem. The marked neu-
trophil toxicity coupled with leukopenia and neutropenia
suggests a possible secondary overwhelming bacterial infec-
tion.
2.) Superimposed stress. The marked lymphopenia is
indicative of high circulating levels of glucocorticoids.
3.)Minimal to mild non-regenerative anemia. Reduction
in red cell mass is so mild that it is probably not clinically
significant at this time. However, red cell data should beclosely monitored to see if anemia develops further. At this
point, it is normocytic, normochromic and non-regenera-
tive.
4.)Thrombocytopenia. Thrombocytopenia may be the
result of a marrow production problem or may reflect pos-
sible DIC associated with overwhelming bacterial infection.
Both a bone marrow evaluation and a full DIC panel arewarranted.
Summary
Hematologic data from this cat are similar to that from
the dog in Case 22, but clear indicators of inflammation are
lacking. This is a case of feline panleukopenia
with secondary bacterial enteritis and endotox-
emia. DIC was confirmed by elevated fibrin split
products, prolonged prothrombin time, and pro-
longed activated partial thromboplastin time.Marrow evaluation revealed a production prob-lem characterized by hypoplasia and necrosis
probably caused by feline panleukopenia virus
infection. Peripheral red cell data do not yet
reflect the production problem because red cell
lifespan is longer than that of leukocytes andplatelets.
Fig. 39 High magnification. Four toxic neutrophils with foamy basophilic cytoplasm
and scattered Döhle bodies. The neutrophil at upper right is a giant form
and has unusual nuclear shape.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 75CASE 24
Signalment: Four-year-old female
Collie-Labrador mix
History: Acute onset lethargy with
pale mucous membranes
HCT 21% WBC 18,000/µl
Hb 7.0 g/dl Bands 1,000/µlRBC 3.1 x 10
6/µl Neutrophils 14,000/µl
TP 6.8 g/dl Lymphocytes 1,500/µlPlatelets Reduced Monocytes 1,500/µl
Reticulocyte count = 4%
Description
Leukogram: There is mild leukocytosis with neu-
trophilia, left shift, marginal lymphopenia, and mild
monocytosis.Erythrogram: There is a moderately severe ane-
mia with reticulocytosis. The absolute reticulocyte
count is 124,000/µl. MCV and MCHC (computed)
are within the reference ranges.
Thrombogram: Thrombocytopenia.Interpretation
1.)Inflammatory leukogram with tissue necrosis.
Neutrophilia with a left shift indicates inflammation. Mild
monocytosis indicates tissue necrosis.
2.)Superimposed stress. Marginal lymphopenia suggests
high circulating glucocorticoids (stress).
3.)Regenerative anemia. Anemia with an absolute retic-
ulocyte count of 124,000/µl is regenerative. Differentiationbetween blood loss and hemolysis is not possible at this
time. The presence of noticeable schizocytes (see Figs. 28,
29) suggests that microangropathic hemolysis is at least
partly responsible.
4.)Possible DIC. The combination of inflammatory
leukogram, thrombocytopenia, and schizocytes on theblood film suggest possible DIC. As in Cases 17 and 18, a
full DIC panel is warranted.
Summary
Considered collectively, hematologic data suggests an
Fig. 40 High magnification. Note the absence of platelets. Three red cell fragments
(schizocytes).Continued

inflammatory process complicated by DIC with
associated regenerative anemia. The anemia maybe complex, possibly resulting from a combination
of blood loss and microangiopathic hemolysis. The
actual diagnosis in this patient was malignant
mammary carcinoma with widespread metastasis.At the time of presentation, there was hemothoraxsecondary to bleeding tumor nodules on the sur-
face of the lung. DIC was also confirmed with
additional laboratory tests.
76
Nestlé PURINA Hemogram Interpretation for Dogs and Cats
Fig. 41 High magnification. Two schizocytes.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 77CASE 25
Signalment: Three-year-old female
Persian cat
History: Chronic, intermittent
cough and occasional
wheezing
HCT 40% WBC 17,000/µl
Hb 13.1 g/dl Neutrophils 10,000/µlRBC 8.0 x 10
6/µl Lymphocytes 2,000/µl
Eosinophils 4,500/µl
Platelets Adequate Monocytes 500/µl
Description
Leukogram: There is a high normal leukocyte count
with a marked eosinophilia.
Erythrogram: Unremarkable.
Thrombogram: Unremarkable.Interpretation
Inflammatory leukogram with systemic hypersensitivity.
Eosinophilia, if persistent, is a clear indicator of both
inflammation and systemic hypersensitivity. In cats, poten-
tial causes include eosinophilic granuloma complex (the
systemic linear plaque form), feline asthma, systemic mast
cell tumor, flea-bite dermatitis, allergic gastroenteritis, and
parasitic infections with a systemic phase. In this case, con-sidering the clinical presentation, feline asthma is at the topof the differential

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 79Part III

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 81Units Dog Cat
Total Protein (TP) g/dl 6.0 – 8.0 6.0 – 8.0
HCT % 37 – 55 30 – 45
Hb g/dl 12 – 18 8 – 15
RBC ×106/µl 5.5 – 8.5 5.0 – 10.0
WBC ×103/µl 6 – 17 6 – 18
Bands /µl 0 – 300 0 – 300
Neutrophils /µl 3,000 – 12,000 3,000 – 12,000
Lymphocytes /µl 1,000 – 5,000 1,500 – 7,000
Monocytes /µl 150 – 1,350 50 – 850
Eosinophils /µl 100 – 1,250 100 – 1,500
MCV fl 60 – 75 40 – 55
MCHC g/dl 32 – 36 30 – 36
Fibrinogen mg/dl 200 – 400 150 – 300
Platelets ×105/µl 2 – 9 3 – 7
Prothrombin Time Seconds 5.5 – 7.9 6.4 – 9.6
Partial
Thromboplastin
Time
(APTT or PTT) Seconds 11.4 – 16.4 9.3 – 18.7
FSPs
(Fibrin/Fibrinogen
Split Products) g/ml <10 <10Hematology Reference Ranges

82 Nestlé PURINA Hemogram Interpretation for Dogs and CatsChapter 1: Leukocytes in Health & Disease
Fig. 1………Normal circulating neutrophils.
Fig. 2 ……..Normal canine eosinophil (left), reactive lym-
phocyte (right).
Fig. 3 ……..Normal feline eosinophil.
Fig. 4………Normal canine basophil.
Fig. 5………Normal canine basophil.
Fig. 6………Normal feline basophil (left), normal neutrophil
(right).
Fig. 7………Normal canine monocytes.
Fig. 8………Normal small lymphocyte (round nucleus),
three neutrophils, and normal band cell (right).
Fig. 9………Blast-transformed (reactive, activated) lympho-
cyte.
Fig. 10…….Reactive lymphocyte (lower center), three neu-
trophils, and a monocyte (top center).
Fig. 11…….Reactive lymphocyte (center) and four neu-
trophils.
Fig. 12…….Reactive lymphocyte.
Fig. 13…….Reactive lymphocyte.
Fig. 14…….Fully differentiated plasma cell.
Fig. 15…….Toxic band cell with foamy, basophilic cyto-
plasm.
Fig. 16…….Giant toxic band with foamy, basophilic cyto-
plasm and giant, irregular nucleus.
Fig. 17…….Two toxic neutrophils and a toxic band. Note
the unusual nuclear shape.
Fig. 18…….Two toxic neutrophils with Döhle bodies.
Fig. 19…….Atypical lymphocyte.Chapter 2: Erythrocytes in Health &
Disease
Fig. 1………Normal canine blood film. Scanning magnifica-
tion. RBCs are uniform in size, shape, and
color, and feature prominent central pallor.
Fig. 2………Canine blood film with increased polychroma-
sia. Scanning magnification. Polychromatophils
are bluish and generally larger than mature
cells.
Fig. 3………High magnification of Fig. 2. This represents a
regenerative anemia with marked polychroma-
sia. Note the marked separation of RBCs.
Fig. 4………Low magnification of a new methylene blue-
stained blood film. Reticulocytes stand out dueto blue stained reticulum visible at this magnifi-
cation. This represents a highly regenerative
anemia.
Fig. 5………High magnification of Fig. 4. Reticulocytes with
precipitated blue reticulum are obvious. Indogs, all would be counted; in cats, only thosewith abundant precipitate (aggregate reticulo-
cytes) would be counted. Several leukocytes arealso present.
Fig. 6………Canine immune-mediated hemolytic anemia.
The anemia is highly regenerative with markedpolychromasia. A spherocyte (arrow).
Fig. 7………A second case of canine immune-mediated
hemolytic anemia with numerous spherocytes.
Fig. 8………Feline immune-mediated hemolytic anemia.
Spherocytes are numerous but less obvious due
to of the lack of central pallor in the normalRBCs.
Fig. 9………Saline-diluted wet preparation demonstrating
autoagglutination.
Fig. 10…….Heinz body hemolytic anemia in the dog.
Several cells with nose-like projections (Heinz
bodies) and several polychromatophils.Index of Figures
All slides courtesy of Alan H. Rebar, DVM, PhD.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 83Fig. 11…….Canine Heinz body hemolytic anemia, new
methylene blue stain. Several cells with Heinz
bodies (upper left). Two reticulocytes with
aggregated reticulum (right center).
Fig. 12…….Feline hyperthyroidism. Numerous cells have
obvious Heinz bodies projecting from their sur-
faces, but anemia is not present.
Fig. 13…….Canine hemobartonellosis. Several cells have
chains of beaded basophilic organisms on their
surfaces. Several polychromatophils and a
schizocyte.
Fig. 14…….Feline hemobartonellosis. Several polychro-
matophils are present. The red cell (center) has
several prominent Hemobartonella bodies.
Fig. 15…….Canine babesiosis. The cell (center) has two
teardrop-shaped organisms. A red cell (upper
right) with a single organism.
Fig. 16…….Microangiopathic hemolysis in disseminated
intravascular coagulopathy (DIC). Numerous
schizocytes.
Fig. 17…….Hepatic hemangiosarcoma in a dog. Two acan-
thocytes (center). A schizocyte (left).
Numerous target cells, which can be precursors
to acanthocytes. Polychromasia indicates a
mildly regenerative anemia.
Fig. 18…….Canine glomerulonephritis. Numerous Burr cells.
Fig. 19…….FeLV(peripheral blood film). Two megaloblasts.
Fig. 20…….Bone marrow smear from the same case as Fig.
19. A large megaloblast (right).
Fig. 21…….Iron deficiency anemia. Numerous red cells
have exaggerated areas of central pallor; some
are smaller than normal. A red cell fragment(schizocyte-center).
Fig. 22…….Myelofibrosis in the dog. A dacryocyte (center
and top center). Numerous ovalocytes.Chapter 5: Case Studies
Fig. 1………Case #4. A band cell with slight toxicity (left).
Note the foamy, granular, slightly basophiliccytoplasm. A normal monocyte (right).
Fig. 2………Case #4. Two band cells and a mature neu-
trophil.
Fig. 3………Case #4. A toxic band cell (left), and a toxic
metamyelocyte (right). The cytoplasm of bothcells is too blue.
Fig. 4………Case #4. A toxic neutrophil with foamy,
basophilic cytoplasm and Döhle bodies.
Fig. 5………Case #5. On scanning magnification, a monocy-
tosis is obvious. Four monocytes and seven neu-
trophils.
Fig. 6………Case #6. A reactive lymphocyte with large
nucleus, lacy chromatin pattern, and basophiliccytoplasm.
Fig. 7………Case #6. Two reactive lymphocytes.
Fig. 8………Case #8. Low magnification reveals a leukocy-
tosis with neutrophilia and left shift.
Fig. 9………Case #8. High magnification. A giant toxic band
cell (center). Note the blue cytoplasm (Wright's
stain x 100).
Fig. 10…….Case #8. Two toxic neutrophils with foamy,
basophilic cytoplasm (Wright's stain x 100).
Fig. 11…….Case #8. A toxic band cell (left), and a toxic
neutrophil (right). Again, note the foamy,
basophilic cytoplasm (Wright's stain x 100).
Fig. 12…….Case #9. Aspirate of a normal lymph node.
Normal small lymphocytes predominate withseveral larger prolymphocytes.
Fig. 13…….Case #9. Aspirate of a lymph node with lym-
phoma. The majority of the cells are large blastswith very large nuclei and prominent nucleoli.
Fig. 14…….Case #10. Low magnification of pleural fluid.
Normal small lymphocytes predominate. Red
cells are seen in the background. This is typicalof a chylous effusion.

84 Nestlé PURINA Hemogram Interpretation for Dogs and CatsFig. 15…….Case #10. High magnification of Fig. 14.
Normal small lymphocytes.
Fig. 16…….Case #11. Two normal eosinophils.
Fig. 17…….Case #13. Scanning magnification. Note the
extremely pale staining of the RBCs.
Fig. 18…….Case #13. High magnification. Note the marked
central pallor of the RBCs. This is typical of
iron deficiency.
Fig. 19…….Case #13. High magnification. A schizocyte
(left center).
Fig. 20-22..Case #14. Numerous RBCs parasitized by
Hemobartonella felis are seen in all three figures.
Both ring forms as well as chains of coccal
forms are present (Wright's stain x 100).
Fig. 23…….Case #15. Scanning magnification. Note the
marked variability in red cell size (anisocytosis).
Fig. 24…….Case #15. Scanning magnification. A left shift
and two nucleated red cells.
Fig. 25…….Case #15. High magnification. Note the pres-
ence of spherocytes. Several polychromatophils
(center). Changes are consistent with immune-
mediated hemolytic anemia.
Fig. 26…….Case #16. Scanning magnification. Monocytosis
is apparent. Red cells exhibit anisocytosis and
polychromasia.
Fig. 27…….Case #16. High magnification. Two polychro-
matophils and nucleated red cells (left).
Numerous red cells have multiple finger-like
projections (acanthocytes). Platelets are obvious.
Fig. 28…….Case #17. Several prominent Heinz bodies
(seen as nose-like projections from the red cell
surface). Note the lack of polychromasia
(Wright's stain x 100).
Fig. 29…….Case #17. With vital stains, Heinz bodies are
much more obvious. In this new methylene
blue-stained preparation, they are seen as blue
precipitates within the red cell (100x).Fig. 30…….Case #18. Scanning magnification.
Poikilocytosis (variable red cell shape) is strik-
ing. Numerous elongated red cells (ovalocytes).
Fig. 31…….Case #18. High magnification. Elongated red
cells with ruffled membranes (Burr cells) have
been associated with metabolic disorders, par-
ticularly renal disease, in humans and dogs.
Fig. 32…….Case #19. Scanning magnification. Numerous
nucleated cells, many of them nucleated redcells. There also appears to be a left shift.
Fig. 33…….Case #19. High magnification. The number of
nucleated red cells is too high for the degree of
polychromasia (inappropriate nucleated red cell
response). Note that the nucleated red cell (cen-
ter) is stippled (contains basophilic cytoplasmic
precipitates). The two neutrophilic bands (left)
have toxic cytoplasm.
Fig. 34…….Case #19. High magnification. The nucleated
red cell (left) is quite immature.
Fig. 35…….Case #19. High magnification. Three nucleated
red cells and a toxic metamyelocyte.
Fig. 36…….Case #20. Low magnification shows large num-
bers of nucleated red cells. Note that the film isvery thin, suggesting severe anemia (Wright's
stain x 50).
Fig. 37…….Case #20. Three metarubricytes, a lymphocyte,
and a nucleated cell that is difficult to classify(Wright's stain x 100).
Fig. 38…….Case #20. Various stages of nucleated red cell
differentiation (Wright's stain x 100).
Fig. 39…….Case #23. High magnification. Three extremely
toxic neutrophil-series cells.
Fig. 40…….Case #24. High magnification. Note the absence
of platelets. Three red cell fragments (schizo-cytes).
Fig. 41…….Case #24. High magnification. Two schizocytes.All slides courtesy of Alan H. Rebar, DVM, PhD.

Nestlé PURINA Hemogram Interpretation for Dogs and Cats 85-A-
activated lymphocytes: Antigen-stimulated (blast-
transformed, reactive) lymphocytes. These lympho-
cytes are actively gearing up to produce antibodies
or lymphokines. They have morphologic features of
active protein producing cells: lacy chromatin (pri-
marily euchromatin) and abundant blue cytoplasm
rich in RNA.
adherence: Stage II of phagocytosis. The binding of
phagocyte surface receptors to microorganisms and
other foreign matter.
autoagglutination: Three-dimensional clumping of ery-
throcytes as a result of cross-linking of erythrocytes
by antibodies; this feature confirms diagnosis of
immune-mediated disease.
-C-
cell-mediated immunity: Refers to the production of
lymphokines of effector T lymphocytes in response
to antigenic stimulation.
chemotaxis: Stage I of phagocytosis. The directed move-
ment of phagocytes along an increasing gradient of
chemoattractant molecules.
-E-
endomitosis: Nuclear division without cytoplasmic divi-
sion. Megakaryoblasts mature to megakaryocytes
via endomitosis.
euchromatin: Chromatin comprised mostly of active
genes (DNA) that control cell function by serving
as templates for messenger RNA (mRNA) forma-
tion, which in turn regulates cellular protein synthe-
sis. Euchromatin has a granular, lacy pattern in
Romanowsky-stained preparations. Monocyte
nuclei contain mostly euchromatin. (In contrast,
heterochromatin contains mostly inactive DNA
whose active sites are bound to histone (protein)suppressors, which inhibit gene activity.
Heterochromatin stains deep purple in
Romanowsky-stained preparations. Neutrophil
nuclei contain primarily heterochromatin.)
erythropoietin: The primary growth factor regulating
committed red cell production and differentiation inthe bone marrow. This hormone is produced pri-
marily in the juxtaglomerular apparatus of the kid-
ney, in response to microenvironmental variations inoxygen tension.
-G-
golgi zones: Membranous perinuclear organelle which is
the primary intracellular site where protein is pack-
aged for secretion.
-H-
Heinz bodies: Precipitates of hemoglobin that occur as a
result of oxidation of hemoglobin. Heinz bodies
often are attached to the inner red cell membrane.
Because they are rigid, fixed precipitates, they causeintravascular lysis as red cells traverse tortuous vas-cular capillary spaces.
humoral immunity: Refers to the production of anti-
bodies directed against specific antigens by effector
B lymphocytes (plasma cells).
-I-
immunocytic system: The "specific immune system"
comprised of the circulating lymphocytes (B lym-phocytes and T lymphocytes). B lymphocytes pro-
duce antibodies while T lymphocytes are responsi-ble for lymphokine production. Lymphocyte prod-
ucts are released in response to specific antigens.
internalization: Stage III of phagocytosis. The process
by which adhered particles (microorganisms) areGlossary of Terms

86 Nestlé PURINA Hemogram Interpretation for Dogs and Catstaken into a phagocyte for killing and digestion.
The process involves invagination of the cell mem-
brane and the formation of a phagocytic vacuole.
-L-
lymphokines: Small, biologically active molecules
released by antigen-stimulated (blast-transformed,
activated, reactive) lymphocytes. These molecules
moderate the immune response and may be capable
of destroying other cells and microorganisms.
Lymphokines are the "molecular hormones" of the
immunocytic system.
-N-
non-specific immune system: Another name for the
phagocytic system. Phagocytes adhere to and ingest
a variety of foreign material on contact.
-O-
opsonization: The process by which microorganisms
and foreign proteins become coated by molecules
for which phagocytes have specific surface recep-
tors. The coating molecules—antibodies and com-
plement fragments—are called opsonins. Once coat-
ed by opsonins, a microorganism or foreign protein
is opsonized. Opsonization facilitates adherence
(stage II of phagocytosis).-P-
phagocytic system: The "non-specific immune system"
comprised of circulating phagocytes: neutrophils
and cells of the monocyte/ macrophage continuum.
These cells establish the first line of defense againstinvading microorganisms.
phagocytosis: The process of ingestion, killing, and
digestion of etiologic agents by cells of the phago-cytic system. Non-living foreign material may alsobe ingested and digested by phagocytes.
polychromatophils: Large, bluish-red cells seen in low
numbers in normal canine and feline blood films.
These immature red cells stain bluish because of a
lower than normal hemoglobin concentration and a
slightly higher than normal amount of cytoplasmicRNA.
polycythemia: Increased circulating red cell mass indi-
cated by elevations in hematocrit, hemoglobin, andtotal red cell count.
polycythemia vera: A myeloproliferative disease char-
acterized by overproduction of all marrow cellular
elements. Clinical findings are generally referable to
increased circulating red cell mass.
-S-
specific immune system: Another name for the
immunocytic system. Immunocyte response is spe-
cific in that antibodies and lymphokines are released
in response to specific antigens.

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