Anatomy of the Colon [301820]

Anatomy of the Colon

The colon is a long tubular organ consisting of muscle and connective tissue with an inner mucosal layer. [anonimizat] (cecum about 7 cm and sigmoid colon about 2.5 cm in diameter).

The overall length is variable with an average length approximating 150 cm. The right and left sides of the colon are fused to the posterior retroperitoneum (secondarily retroperitonealized) while the transverse colon and sigmoid colon are relatively free within the peritoneum. The transverse colon is held in position via its attachments to the right/left colon at the flexures ([anonimizat]) (Figure 1 )and is further fused to the omentum. Generally speaking the colon is located peripherally within the abdomen with the small bowel located centrally.

There are three important anatomic points of differentiation between the colon and the small intestine:

[anonimizat],

the haustra.

[anonimizat]. [anonimizat] (unlike the omentum on the stomach). [anonimizat]. This outer layer of muscle is indeed circumferentially complete [ 1], but is considerably thicker in three areas represented by the taenia.

The three taeniae have been given separate names by some: [anonimizat], and taenia omentalis for posterolateral band. The bands are continuous from their origin at the base of the appendix until the rectosigmoid junction where they converge (marking an anatomically identifiable differentiation between the sigmoid colon and rectum). [anonimizat]. This difference in length results in outpouchings of the bowel wall between the taenia referred to as haustra.The haustra are further septated by the plicae semilunares.

Cecum

The proximal most portion of the colon is termed the cecum, a sac-like segment of colon below (proximal to) the ileocecal valve. [anonimizat] 8 cm in length and 7 cm in diameter. At its base is the appendix. Terminating in the posteromedial area of the cecum is the terminal ileum (ileocecal valve). [anonimizat] (upper or distal cecum). The ileocecal valve is a circular muscular sphincter which appears as a slit-like (“fish-mouth”) opening noted on an endoscopic evaluation of the cecum. [anonimizat], its competence leads to the urgency of a colon obstruction as it develops into a closed-loop obstruction. Regulation of ileal emptying into the colon appears to be the prime task in ileocecal valve function [ 2 ].

[anonimizat]. The appendiceal orifice is generally about 3–4 cm from the ileocecal valve. The appendix itself is of variable length (2–20 cm) and is about 5 [anonimizat]. Blood is supplied to the appendix via the appendiceal vessels contained within the mesoappendix. This results in the most common location of the appendix being medially on the cecum toward the ileum, but the appendix does have great variability in its location including pelvic, retrocecal, preileal, retroileal, and subcecal.

Ascending Colon

From its beginning at the ileocecal valve to its terminus at the hepatic flexure where it turns sharply medially to become the transverse colon, the ascending colon measures on average, about 15–18 cm. Its anterior surface is covered in visceral peritoneum while its posterior surface is fused with the retroperitoneum. The lateral peritoneal reflection can be seen as a thickened line termed the white line of Toldt, which can serve as a surgeon’s guide for mobilization of the ascending colon off of its attachments to the retroperitoneum, most notably the right kidney (Gerotta’s fascia) and the loop of the duodenum located posterior and superior to the ileocolic vessels.

Transverse Colon

The transverse colon traverses the upper abdomen from the hepatic flexure on the right to the splenic flexure on the left. It is generally the longest section of colon (averaging 45–50 cm) and swoops inferiorly as it crosses the abdomen. The entire transverse colon is covered by visceral peritoneum, but the greater omentum is fused to the anterosuperior surface of the transverse colon. Superior to the transverse mesocolon, inferior to the stomach, and posterior to the omentum is the pocket of the peritoneal cavity termed the lesser sac, with the pancreas forming the posterior most aspect. The splenic flexure is the sharp turn from the transversely oriented transverse colon to the longitudinally oriented descending colon. It can be adherent to the spleen and to the diaphragm via the phrenocolic ligament.

Descending Colon

The descending colon travels inferiorly from the splenic flexure for the course of about 25 cm. It is fused to the retroperitoneum (similarly to the ascending colon) and overlies the left kidney as well as the back/retroperitoneal musculature. Its anterior and lateral surfaces are covered with visceral peritoneum and the lateral peritoneal reflection (white line of Toldt) is again present.

Sigmoid Colon

The sigmoid colon is the most variable of the colon segments. It is generally 35–45 cm in length. It is covered by visceral peritoneum, thereby making it mobile. Its shape is considered “omega-shaped” but its configuration and attachments are variable. Its mesentery is of variable length, but is fused to the pelvic walls in an inverted-V shape creating a recess termed the intersigmoid fossa.Through this recess travel the left ureter, gonadal vessels, and often the left colic vessels.

Rectosigmoid Junction

The end of the sigmoid colon and the beginning of the rectum is termed the rectosigmoid junction. It is noted by the confluence of the taeniae coli and the end of epiploicae appendices. While some surgeons have historically considered the rectosigmoid junction to be a general area (comprising about 5 cm of distal sigmoid and about 5 cm of proximal rectum), others have described a distinct and clearly defined segment. It is the narrowest portion of the large intestine, measuring 2–2.5 cm in diameter. Endoscopically, it is noted as a narrow and often sharply angulated area above the relatively capacious rectum, and above the three rectal valves.

Anatomical Relations

The colon has numerous important anatomical relations in the abdomen, as shown in Table I:

Table I Anatomical relations of the colon

Blood Supply

Arterial supply

The colon receives blood supply from two main sources, branches of the Inferior Mesenteric Artery (IMA) (descending and sigmoid colon) (Figure 2 )and branches of the Superior Mesenteric Artery (SMA) (cecum, ascending, and transverse colon) .

There is a watershed area between these two main sources located just proximal to the splenic flexure where branches of the left branch of the middle colic artery anastomose with those of the left colic artery. This area represents the border of the embryologic midgut and hindgut. Though the blood supply to the colon is somewhat variable, there are some general common arteries. The cecum and right colon are supplied by the terminus of the SMA, the ileocolic artery .

The right colic artery is less consistent and, when present, can arise directly from the SMA, from the ileocolic, or from other sources. The transverse colon is supplied via the middle colic artery, which branches early to form right and left branches.

The middle colic artery originates directly from the SMA. The left colon and sigmoid colon are supplied by branches of the IMA, namely the left colic and a variable number of sigmoid branches. After the final branches to the sigmoid colon, the IMA continues inferiorly as the superior hemorrhoidal (rectal) artery.

Superior Mesenteric Artery

The superior mesenteric artery (SMA) is the second, unpaired anterior branch off of the aorta (Figure 2 ). It arises posterior to the upper edge of the pancreas (near the L1 vertebrae), courses posterior to the pancreas, and then crosses over the third portion of the duodenum to continue within the base of the mesentery. From its left side, the SMA gives rise to up to 20 small intestinal branches while the colic branches originate from its ride side. The most constant of the colic branches is the ileocolic vessel which courses through the ascending mesocolon where it divides into a superior (ascending) branch and an inferior (descending) branch [ 3 ]. A true right colic artery is absent up to 20% of the time and, when present, typically arises from the SMA. Alternatively, the right colic artery can arise from the ileocolic vessels or from the middle colic vessels [ 3 , 4 , 5 ]. The middle colic artery arises from the SMA near the inferior border of the pancreas. It branches early to give off right and left branches. The right branch supplies the hepatic flexure and right half of the transverse colon. The left branch supplies the left half of the transverse colon to the splenic flexure. In up to 33% of patients, the left branch of the middle colic artery can be the sole supplier of the splenic flexure [ 3 , 6 ].

Inferior Mesenteric Artery

The inferior mesenteric artery (IMA) (Figure 2 ) is the third unpaired, anterior branch off of the aorta, originating 3–4 cm above the aortic bifurcation at the level of the L2 to L3 vertebrae. As the IMA travels inferiorly and to the left, it gives off the left colic artery and several sigmoidal branches. After these branches, the IMA becomes the superior hemorrhoidal (rectal) artery as it crosses over the left common iliac artery. The left colic artery divides into an ascending branch (splenic flexure) and a descending branch (the descending colon). The sigmoidal branches form a fairly rich arcade within the sigmoid mesocolon (similar to that seen within the small bowel mesentery). The superior hemorrhoidal artery carries into the mesorectum and into the rectum. The superior hemorrhoidal artery bifurcates in about 80% of patients.

The Marginal Artery and Other Mesenteric Collaterals

The major arteries noted above account for the main source of blood within the mesentery. However, the anatomy of the mesenteric circulation and the collaterals within the mesentery remain less clear. Haller first described a central artery anastomosing all mesenteric branches in 1786 [ 7 ]. When Drummond demonstrated its surgical significance in the early twentieth century, it became known as the marginal artery of Drummond [ 8 , 9 ]. The marginal artery (Figure 2 ) has been shown to be discontinuous or even absent in some patients, most notably at the splenic flexure (Griffiths’ critical point), where it may be absent in up to 50% of patients [ 10 ]. This area of potential ischemia is the embryologic connection between the midgut and hindgut. Inadequacy of the marginal artery likely accounts for this area being most severely affected in cases of colonic ischemia. Another potential (though controversial) site of ischemia is at a discontinuous area of marginal artery located at the rectosigmoid junction termed Sudeck’s critical point. Surgical experience would question whether this potential area of ischemia exists; a recent fluorescence study indicates that it does [ 11 ], though its clinical importance remains in doubt.

Venous Drainage

Venous drainage of the colon largely follows the arterial supply with superior and inferior mesenteric veins draining both the right and left halves of the colon (Figure 3 ). They ultimately meet at the portal vein to reach the intrahepatic system. The superior mesenteric vein (SMV) travels parallel and to the right of the artery. The inferior mesenteric vein (IMV) does not travel with the artery, but rather takes a longer path superiorly to join the splenic vein. It separates from the artery within the left colon mesentery and runs along the base of the mesentery where it can be found just lateral to the ligament of Treitz and the duodenum before joining the splenic vein on the opposite (superior) side of the transverse mesocolon. Dissecting posterior to the IMV can allow for separation of the mesenteric structures from the retroperitoneal structures during a medial-to-lateral dissection.

Lymphatic Drainage

The colon wall has a dense network of lymphatic plexuses.These lymphatics drain into extramural lymphatic channels which follow the vascular supply of the colon. Lymph nodes are plentiful and are typically divided into four main groups. The epiploic group lies adjacent to the bowel wall just below the peritoneum and in the epiploicae. The paracolic nodes are along the marginal artery and the vascular arcades. They are most filtering of the nodes. The intermediate nodes are situated on the primary colic vessels. The main or principal nodes are on the superior and inferior mesenteric vessels. Once the lymph leaves the main nodes, it drains into the cisterna chili via the para-aortic chain.

Nervous Innervation

The colon is innervated by the sympathetic and parasympathetic nervous systems and closely follows the arterial blood supply. The sympathetic innervation of the right half of the

colon originates from the lower six thoracic splanchnic nerves which synapse within the celiac, pre-aortic, and superior mesenteric ganglia. The post-ganglionic fibers then follow the SMA to the right colon. The sympathetic innervation for the left half originates from L1, L2, and L3. Parasympathetic fibers to the right colon come from the posterior (right) branch of the Vagus Nerve and celiac plexus. They travel along the SMA to synapse with the nerves within the intrinsic autonomic plexuses of the bowel wall. On the left side, the parasympathetic innervation comes from S2, S3, and S4 via splanchnic nerves.

Embryology of the colon

The embryologic development of the GI system is complex.That said, however, a working knowledge of the development of the small bowel, colon, and anorectum is critical for a colorectal surgeon as it can aid in understanding pathophysiology and is essential for recognizing surgical planes.

The endodermal roof of the yolk sac develops into the primitive gut tube. This initially straight tube is suspended upon a common mesentery. By week 3 of development, it has three discernible segments; namely the foregut, midgut, and hindgut. The midgut starts below the pancreatic papilla to form the small intestine and the first half of the colon (all supplied by the superior mesenteric artery). The distal colon and rectum, as well as the anal canal develop from the hindgut and are therefore supplied by the inferior mesenteric artery. There is a normal process by which the intestinal tract rotates . The first stage is the physiologic herniation of the midgut, the second stage is its return to the abdomen, and the third stage is the fixation of the midgut. Abnormalities in this normal process lead to various malformations (see below). The physiologic herniation (first stage) occurs between weeks 6 and 8 of development. The primitive gut tube elongates over the superior mesenteric artery and bulges out through the umbilical cord

During the eighth week, these contents move in a counterclockwise fashion, turning 90° from the sagittal to the horizontal plane

Anomalies at this stage are rare, but include situs inversus, duodenal inversion, and extroversion of the cloaca. During the second stage (tenth week of gestation), the midgut loops return to the peritoneal cavity and simultaneously rotate an additional 180° in the counterclockwise direction. The pre-arterial portion of the duodenum returns to the abdomen first, followed by the counterclockwise rotation around the superior mesenteric vessels, resulting in the duodenum lying behind them. The colon returns after the rotation, resulting in their anterior location.

Anomalies in this stage are more common and result in non-rotation, malrotation, reversed rotation, internal hernia, and omphalocele. The third stage (fixation of the midgut) begins once the intestines have returned to the peritoneal cavity and end at birth. The cecum migrates to the right lower quadrant from its initial position in the upper abdomen.

After the completion of this 270° counterclockwise rotation, fusion begins, typically at week 12–13. This results in fusion of the duodenum as well as the ascending and descending colon (Figure 4 ).

Major Anomalies of Rotation

Non-rotation

The midgut returns to the peritoneum without any of the normal rotation. This results in the small intestine being on the right side of the abdomen and the colon on the left side (Figure 5). This condition can remain asymptomatic (a finding noted at laparoscopy or laparotomy) or result in volvulus affecting the entirety of the small intestine. The twist generally occurs at the duodenojejunal junction as well as the midtransverse colon.

Malrotation

There is normal initial rotation, but the cecum fails to complete the normal 270° rotation around the mesentery. This results in the cecum being located in the mid-upper abdomen with lateral bands (Ladd’s bands) fixating it to the right abdominal wall (Figure 6 ). These bands can result in extrinsic compression of the duodenum

Reversed Rotation

Clockwise (rather than counterclockwise) rotation of the midgut results in the transverse colon being posterior to the superior mesenteric artery while the duodenum lies anterior to it.

Omphalocele

An omphalocele is, basically, the retention of the midgut within the umbilical sac and its failure to return to the peritoneal cavity.

Internal Hernias

Internal hernias , as well as congenital obstructive bands, can cause congenital bowel obstructions. These are considered failures of the process of fixation (the third stage of rotation).This can be the result of an incomplete fusion of the mesothelium or when structures are abnormally rotated. Retroperitoneal hernias can occur in various positions, most notably paraduodenal, paracecal, and intersigmoid.

Other Congenital Malformations of the Colon and Small Intestine

Proximal Colon Duplication

There are three general types of colonic duplication: mesenteric cysts, diverticula, and long colon duplication [ 12 ]. Mesenteric cysts are lined with intestinal epithelium and variable amounts of smooth muscle. They are found within the colonic mesentery or posterior to the rectum (within the mesorectum). They may be closely adherent to the bowel wall or separate from it. They generally present as a mass or with intestinal obstruction as they enlarge. Diverticula can be found on the mesenteric or anti-mesenteric sides of the colon and are outpouchings of the bowel wall. They often contain heterotopic gastric or pancreatic tissue. Long colonic duplications of the colon are the rarest form of duplication. They parallel the functional colon and often share a common wall throughout most of their length. They usually run the entire length of the colon and rectum and there is an association with other genitourinary abnormalities.

Meckel’s Diverticulum

A Meckel’s diverticulum is the remnant of the vitelline or omphalomesenteric duct (Figure 1-13 ). It arises from the antimesenteric aspect of the terminal ileum, most commonly within 50 cm of the ileocecal valve. They can be associated with a fibrous band connecting the diverticulum to the umbilicus (leading to obstruction) or it may contain ectopic gastric mucosa or pancreatic tissue (leading to bleeding or perforation)

Atresia of the Colon

Colonic atresia, representing only 5% of all gastrointestinal atresias, is a rare cause of congenital obstruction. They are likely the result of vascular compromise during development [ 13 ]. They vary in severity from a membranous diaphragm blocking the lumen to a fibrous cord-like remnant, on to a complete absence of a segment [ 14 ].

Hirschsprung’s Disease

This nonlethal anomaly, which is more common in males, results from the absence of ganglion cells within the myenteric plexus of the colon. It is caused by interruption of the normal migration of the neuroenteric cells from the neural crest before they reach the rectum. This results in dilation and hypertonicity of the proximal colon

Anorectal Malformations

Abnormalities in the normal development of the anorectum can be attributed to “developmental arrest” at various stages of normal development. These abnormalities are often noted in concert with spinal, sacral, and lower limb defects, as noted by Duhamel and theorized to be related to a “syndrome of caudal regression” [ 15 ].

Anal Stenosis

While anal stenosis in a newborn is relatively common, noted in 25–39% of infants, symptomatic stenosis is only noted in 25% of these children [ 16 ]. The majority of these children undergo spontaneous dilation in the first 3–6 months of life.

Membranous Atresia

This very rare condition is characterized by the presence of a thin membrane of skin between the blind end of the anal canal and the surface. It is also termed the covered anus. It is more common in males.

Anal Agenesis

The rectum develops to below the puborectalis where it either ends in an ectopic opening (fistula) in the perineum, vulva, or urethra, or it ends blindly (less commonly). The sphincter is present at its normal site.

Anorectal Agenesis

Anorectal agenesis is the most common type of “imperforate anus.” More common in males, the rectum ends well caudal to the surface and the anus is represented by a dimple with the anal sphincter usually being normal in location. In most cases, there is a fistula to the urethra or vagina. High fistulae (to the vagina or urethra) with anorectal agenesis develop as early as the sixth or seventh week of gestation while the low fistulae (perineal) or anal ectopia develop later, in the eighth or ninth week of development.

Rectal Atresia or “High Atresia ”

In rectal atresia, the rectum and the anal canal are separated from one another by an atretic portion. It is embryologically the distal most type of colon atresia, but is still considered an anorectal disorder clinically.

Persistent Cloaca

This rare condition, which only occurs in female infants, is the result of total failure of descent of the urorectal septum. It occurs at a very early stage of development.

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Colon cancer

Colon cancer is a type of cancer that begins in the large intestine (colon). The colon is the final part of the digestive tract .Colon cancer can happen at any age but it typically affects older adults It starts like a small, noncancerous (benign) clumps of cells known as polyps that are usually formed on the form on the inside of the colon. With the time passing by, some of these polyps can become colon cancers.[17]

Polyps usually produce few symptoms. Doctors recommend regular screening tests to help prevent colon cancer in order to not let polyps turn into cancer.

If colon cancer develops, there are means of treatment for solving the condition, including surgery, radiation therapy and drug treatments, such as chemotherapy, targeted therapy and immunotherapy.

Symptoms

Usually symptoms of colon cancer are not present until the cancer becomes more severe. Screening tests for colon cancer are important for people 50 and older.

Having any of this symptoms, people should immediate seek medical help:

Seeing bleeding from the rectum or blood mixed with stool. It is usually(but not always) detected through a fecal occult (hidden) blood test,

The presence of fatigue and pale skin due to the anemia.

Rectal bleeding can be hidden and chronic and the only guidance is the iron deficiency anemia.

Changes in the frequency of bowel movement

If the tumor gets large enough, it may partially or completely block the colon. The following symptoms can explain a bowel obstruction:

Unexplained, persistent nausea or vomiting

Unexplained weight loss

Abdominal distension:

Abdominal pain: It is not usually presented in colon cancer. One cause of happening so, is the perforation of the bowel. Having the bowel contents into the pelvis can cause infection and inflammation (peritonitis).

Change in frequency or character of stool (bowel movements)

Narrow or ribbon-like stools

Constipation

Sensation of incomplete evacuation after a bowel movement

Rectal pain

Causes

It is not know the most found etiology for the colon cancers. Colon cancer begins when healthy cells from the colon start to develop mutations in their DNA. A cell's DNA contains a set of instructions that tell a cell what to do.

Healthy cells grow and divide in order to maintain balance for the normal functioning. When a cell's DNA becomes cancerous, cells continue to divide in a chaotic way. When the cells accumulate, they form a tumor. The cancer cells can grow to invade and destroy normal tissue and the cancerous cells can travel to other parts of the body forming metastasis.

Risk factors

There are many factors that may increase the risk of colon cancer include:

Inherited syndromes that bring a higher risk of colon cancer. There are gene mutations that passed through generations of the familyand that can increase the risk of colon cancer significantly. There is a small percentage of colon cancers are connected to inherited genes. The most found inherited syndromes that brings a higher risk of colon are Lynch syndrome, known as hereditary non-polyposis colorectal cancer (HNPCC) and familial adenomatous polyposis (FAP)

African-American race. The Afro-Americans have high risk of colon cancer compared to people from other races.

Elderly. Colon cancer can be diagnosed at any age, but a majority of people with colon cancer are older than 50. The rates of colon cancer in people younger than 50 have been increasing, but the reason for this is not known.

A history of polyps or colorectal cancer. For the patients that had colon cancer or noncancerous colon polyps, having a higher risk of colon cancer for the future.

Inflammatory intestinal conditions. Ulcerative colitis and Crohn's disease (Chronic inflammatory diseases), can increase the risk of colon cancer.

Family history of colon cancer. Patients are more likely to develop colon cancer if they have a blood relative who has had the disease. If more than one family member has colon cancer or rectal cancer, the risk is even greater.

Low-fiber, high-fat diet. Colon cancer is usually associated with Western diet, which is a diet that is low in fiber and high in fat and calories. There were studies that explained that some of the people that are eating red meat and processed met have a higher risk of colon cancer.

Diabetes. People presenting diabetes or having insulin resistance get an increased risk of colon cancer.

Smoking. People that smoke can get an increased risk of colon cancer.

Alcohol. An increased use of alcohol increases your risk of colon cancer.

A sedentary lifestyle. People who are inactive are more likely to develop colon cancer. A reduction of the risk of colon cancer is had by getting regular exercises.

Obesity. People with high BMI in the intervals of obesity, have an increased risk of colon cancer and an increased risk of dying of colon cancer, comparing them with people with normal weight.

Radiation therapy for cancer.

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Some things patients cannot influence are:

The age – most people with it are older than 50

Polyps or inflammatory bowel disease

precancerous colon polyps or family history of colorectal cancer

Colorectal Cancer: Stages

Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting other parts of the body.

Doctors use diagnostic tests to find out the cancer's stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancer.

TNM staging system

One tool that doctors use to describe the stage is the TNM system. (Fig,7 )

The completeness of resection designation is seen in Figure 8.

Grade (G)

Doctors also describe this type of cancer by its grade (G). The grade describes how much cancer cells look like healthy cells when viewed under a microscope.

The doctor compares the healthy tissue with cancerous tissue. Healthy tissue usually contains different types of cells grouped together. When cancer looks similar to healthy tissue and contains different cell groupings, it is called "differentiated" or a "low-grade tumor." If the cancerous tissue looks very different from healthy tissue, it is called "poorly differentiated" or a "high-grade tumor." The cancer’s grade may help the doctor predict how quickly the cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.

GX: The tumor grade cannot be identified.

G1: The cells are more like healthy cells (called well differentiated).

G2: The cells are somewhat like healthy cells (called moderately differentiated).

G3: The cells look less like healthy cells (called poorly differentiated).

G4: The cells barely look like healthy cells (called undifferentiated).

Cancer stage grouping

Doctors assign the stage of the cancer by combining the T, N, and M classifications.(Fig 9 )

Stage 0: This is called cancer in situ. The cancer cells are only in the mucosa, or the inner lining, of the colon or rectum.

Stage I: The cancer has grown through the mucosa and has invaded the muscular layer of the colon or rectum. It has not spread into nearby tissue or lymph nodes (T1 or T2, N0, M0).

Stage IIA: The cancer has grown through the wall of the colon or rectum and has not spread to nearby tissue or to the nearby lymph nodes (T3, N0, M0).

Stage IIB: The cancer has grown through the layers of the muscle to the lining of the abdomen, called the visceral peritoneum. It has not spread to the nearby lymph nodes or elsewhere (T4a, N0, M0).

Stage IIC: The tumor has spread through the wall of the colon or rectum and has grown into nearby structures. It has not spread to the nearby lymph nodes or elsewhere (T4b, N0, M0).

Stage IIIA: The cancer has grown through the inner lining or into the muscle layers of the intestine. It has spread to 1 to 3 lymph nodes or to a nodule of tumor in tissues around the colon or rectum that do not appear to be lymph nodes but has not spread to other parts of the body (T1 or T2, N1 or N1c, M0; or T1, N2a, M0).

Stage IIIB: The cancer has grown through the bowel wall or to surrounding organs and into 1 to 3 lymph nodes or to a nodule of tumor in tissues around the colon or rectum that do not appear to be lymph nodes. It has not spread to other parts of the body (T3 or T4a, N1 or N1c, M0; T2 or T3, N2a, M0; or T1 or T2, N2b, M0).

Stage IIIC: The cancer of the colon, regardless of how deep it has grown, has spread to 4 or more lymph nodes but not to other distant parts of the body (T4a, N2a, M0; T3 or T4a, N2b, M0; or T4b, N1 or N2, M0).

Stage IVA: The cancer has spread to a single distant part of the body, such as the liver or lungs (any T, any N, M1a)

Stage IVB: The cancer has spread to more than 1 part of the body (any T, any N, M1b).

Stage IVC: The cancer has spread to the peritoneum. It may also have spread to other sites or organs (any T, any N, M1c).

Recurrent: Recurrent cancer is cancer that has come back after treatment. The disease may be found in the colon, rectum, or in another part of the body. When the cancer returns,there are usually made other tests,often similar to those done at the time of the original diagnosis.

Histopathologic diagnosis of colorectal carcinoma

More than 90% of colorectal carcinomas are adenocarcinomas tthat are originated from epithelial cells of the colorectal mucosa [18]. Other types of colorectal carcinomas include adenosquamous, squamous cell, neuroendocrine, spindle cell and undifferentiated carcinomas.

Adenocarcinoma is characterized by glandular formation, which is the basis for histologic tumor grading.

In well differentiated adenocarcinoma >95% of the tumor is gland forming.

Moderately differentiated adenocarcinoma shows 50-95% gland formation.

Poorly differentiated adenocarcinoma is mostly solid with <50% gland formation.

In practice, most colorectal adenocarcinomas (~70%) are diagnosed as moderately differentiated (Figure 10).[19,20] Well and poorly differentiated carcinomas account for 10% and 20%, respectively.

The majority of colorectal carcinomas are diagnosed by polypectomy or endoscopic biopsy. The important aspect of microscopic examination is to find evidence of invasion. This can be difficult when the biopsy is superficial or poorly oriented. It is important to see whether the muscularis mucosae is disrupted by neoplastic cells.Invasive carcinoma typically invades through the muscularis mucosae into the submucosa. Another important feature of invasion is the presence of desmoplasia or desmoplastic reaction (Figure 11), a type of fibrous proliferation surrounding tumor cells secondary to invasive tumor growth.

Invasive colorectal carcinoma shows most of the times characteristic necrotic debris in glandular lumina, so-called “dirty necrosis” (Figure 12). This feature can be useful to suggest a colorectal primary when a metastasis of unknown origin is found.[21]

Prevention

Screening colon cancer

Doctors recommend that people with an average risk of colon cancer consider colon cancer screening around age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner.(Table II )Several screening options exist — each with its own benefits and drawbacks..(Table III)

Table II American Cancer Society Guidelines on Screening and Surveillance for the Early Detection of Colorectal Adenomas and Cancer for Increased Risk or High Risk22

Source: https://www.cancer.org/health-care-professionals/american-cancer-society-prevention-early-detection-guidelines.html

Table III

Source: https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/screening-tests-used.html

Lifestyle changes

To reduce the risk of colon cancer ,patients can make changes in their everyday life. Some of them are presented:

Stop smoking.

Exercise most days of the week. get at least 30 minutes of exercise on most days. If patients are inactive, they should start slowly and build up gradually to 30 minutes

Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention.

Drink alcohol in moderation. (limit the amount of alcohol they drink to no more than one drink a day for women and two for men.)

Maintain a healthy weight. If patients have a healthy weight, they should work to maintain the weight by combining a healthy diet with daily exercise. Patients aim to lose weight slowly by increasing the amount of exercise they get and reduce the number of calories they eat.

Colon cancer prevention for people with a high risk

Some medications have been found to reduce the risk of precancerous polyps or colon cancer. For instance, some evidence links a reduced risk of polyps and colon cancer to regular use of aspirin or aspirin-like drugs. Taking aspirin daily has some risks, including gastrointestinal bleeding and ulcers.

These options are generally reserved for people with a high risk of colon cancer. There is not enough evidence to recommend these medications to people who have an average risk of colon cancer.

Complications of colon cancer

If we have no fast diagnosis and also if it is not applied a proper treatment for the colon cancer,this disease will evolve and it will bring complications with exitus at the end stage.

Step-by step the tumor will have a loco-regional extension, and then will have a distance metastasis. An excessive development of the tumor, exceeds the vasculo-genesis capacity, and there will be some hypo-irigated zones. Later the necrosis will cause hemorrhage and perforations. There are also cases when the tumor cause bowel obstruction because it obstructs the lumen.The tumoral cells are in direct contact with the lymph and venous circulation in the sub-mucous once the local barrier representing the basal membrane of the mucous is infiltrated .

The complications triggered by colon tumors can be local or distant.

1.The main local complications are:

hemorrhage,

tumoral supra-infections and suppuration,

perforation and colic stenosis.

Hemorrhage: it happens because of tumoral friability that makes the neoplastic tissue to defragment. It usually appears when there are vegetant tumors and it has a predilection for the right colon. The bleeding is low and repeated, chronic, blood being mixed with feces; as a result anemia occurs.

Suprainfection of the tumor: is a result of the tumoral necrobiosis processes, that bring devitalized areas where the microbial factor can be grafted. There are moments when palpation of the tumoral formation can be obtained. A special concern is given to the appearance of fever,when it is a requirement for further investigation

Stenosis occurs when there are cases of infiltrative tumors, and it has a predilection for the left colon and colon flexes. The specific features of low patent obstruction are sometimes preceded by a sub-occlusive syndrome.

Colic perforations can be

local, at the tumor level,

at distance ( diastatic by colic wall penetration as a result of higher intralumenal pressure).

Diastatic perforations occurs at the cecoascending's level, that is the segment with the thinnest wall and the largest diameter. The requests for diastatic perforation occurrence is a competent iliocaccal valve which allows to achieve a high intralumenal pressure in a colic segment that is obstructed at both ends at the tumoral stenosis level and at the valve level.

2. Loco-regional extension:

Extension is done step-by-step, by perineural way or by intralumenal seeding (usually after the surgery being done). There are a lot of cases when the urethra is interested, and usually urethero-hydronephrosis occurs; the transverse colon tumors invade the stomach , the sigmoid tumors case invade the left annex, the uterus and the bladder, small loops with a result of enterocolic necroses or fistula.

There are also general tumor consequence and they are usually considered distance complications.

Distance metastasis may occur via the lymph or via the venous path.There will be a production of liver, lung, brain or bone metastases with the lymph nodes being involved.

Deep venous thromboses: caused by the endothelial lesions induced by chemotherapy or by the thrombogene factors released by the tumoral mass

Multiple deep thrombophlebitis –Trousseau's sign – are part of the paraneoplastic syndrome. pulmonary thromboembolism or pylo-phlebitis can also be associated.

Anemia is a result of the chronic bleeding .

Neoplastic cachexia: occurs at the terminal stages.

Treatment for colon cancer

MEDICAL TREATMENT

The role of this treatment is to restore in the pre-operative period the equilibrium of the systems up to a level as for the body could stand anesthesia and surgery itself. [23]Before the programmed operations it should always be take care of : the rebalance anemia by iso group blood,iso Rh factor transfusion ,for diabetics to reevaluate the glucose levels and get them below 180mg/100 ml using insulin, to address cardio-circulatory dysfunctions and the respiratory conditions as well as the possible kidney or hepatic failures. When it comes to emergency situations, the preoperative time is shortened because it is a really need of surgery and aims at restoring the biological constants to values that would make the anesthetic and surgical acts possible.

In the case of obstructive tumors and perforations, food intake( per oral) is stopped, and the patient usually get a nasogastric tube in order to prevent vomiting, to remove digestive fluids, and to help to monitor the fluid loss which needs to be compensated. Also a urinary catheter can help with monitoring the fluid loss. Energy needs ,hydration and electrolytic-acid base balance are provided using saline solution intra venous . Glucose solution, macromolecular Dextran type solution; ringer solution, nutritive products are administered endovenously. There is also a large spectrum antibiotics that are used, to prevent septic dissemination caused by colon microbism.

When there are heavy,shock generating bleeding, the filling of the vascular system must be done almost in the same with the surgery that attempts to stop the hemorrhage In such situations the nasogastric tube helps a lot because it allows – apart from its other functions – to perform differential diagnosis from a high digestive hemorrhage.

PROPHILACTIC TREATMENT BY ANTIBIOTICS:

The reason why this is a very important factor is the fact that it eliminates the contamination of the body made by the extremely abundant and virulent microbial flora of the colon. Antibiotics are used in order to fight off local intraoperative contamination of the peritoneum by decreasing the intraluminal microbism and also to prevent systemic contamination .

Antibioprophilaxy is achieved by an increased antibiotic titre that covers a wide spectrum of the colon and the colon flora . Antibiotics are administered (preoperatively or upon anesthesia induction) in a single dose per day of 4th generation cephalosporins (cefepima, ceftibuten, cepiroma -cefrom,). If that generation of cephalosporins is not found, 2nd generation cephalosporins (cefuroxim) or antibiotics against gram-negative germs (gentamicin, kanamicin) can be associated with metronidazol for anaerob coverage.

COLON PREPARATION:

There are numerous septic complications and anastomotic fistulas that may occur after colon surgery and their number decrease in direct proportion with the number of germs.

There were studies that have demonstrated the absence of any statistically significant difference between the rates of post-operative complications on the colon mechanically prepared or not prepared at all.

A proper preparation of the colon has to be with hydric diet with at least 7 days before the intended surgery; a number of cleansing enemas is given on the day before surgery to the patient. At the moment, the most used method of mechanical colon cleansing consists in its washout by having an oral intake of different substances: 50 % diluted mannitol – approx. 1 1 two days before surgery, Fortrans- 4 1 of diluted solution (1 package of powder in 1 1 of water) 24 hrs before surgery, polietylene-glycol solution – 41 the day before surgery, lactulose, X-prep. Sometimes laxatives can be administered(when the intake of a large quantity of liquid is not tolerated): Dulcolax 12 tablets pre-op sometimes in association with magnesium citrate.

When there are difficult situations,emergency situation with obstruction or perforation, the colon mechanical preparation is not possible preoperatively: it is performed intraoperatively either by colon washout through a tube inserted at the caecum level, or by retrograde colon emptying through a Faucher tube mounted in the stomach (MonksMoynihan maneuver).

THROMBOEMBOLIC DISEASE PROPHILAXIS:

The most exposed to this type of complication are the patients with a positive history of antecedent thromboembolic condition, the elderly and the obese .Prophylaxis is done both postoperatively by administration of heparin or small-molecule heparins (clexan) and intraoperatively by using compressive bands which can automatically compress the patient's calves.

SURGICAL TREATMENT

ONCOLOGICAL OPERATIONS: also called curative or radical, whose purpose is to cure the neoplasm and its distance and local consequences eradication, and also to prevent recurrence. It is a must to remove the tumor along with a safety colon segment and to raise the lymph node territory corresponding to the colon segment. It concludes that this type of operations are related to the early stages of the disease, when the lymph dissemination is limited and when the surgeon can remove the tumor. Knowing the tumor location at a certain colon level, there were developed many several standardized operations, that meet the oncological surgery requirements[23]

RIGHT HEMICOLECTOMY: is usually recommended for the right colon tumors – 2 surgical terms defining the colon irrigated by the right branch of the medium colic, namely: cecum, ascending colon, the hepatic angle of the colon and the proximal part of the transverse colon and the ileobicecoappendicular arteries. For the last part of the terminal ileum, between the ileobicecoappendicular artery and the last ileal artery,there is a paucivascular area( the Treves) which is the reason for a weak vascularization of this ileal segment and this can make it impossible to be used for anastomosis.

Because of this, the last part of the terminal ileum is resected as a block with the other above mentioned colon segments; usually the bowel transit will be restored later by an anastomosis which can be done in several manners: terminolateral, termino-terminal, latero-lateral. The lymph node territory in the proximity of vascularization should be raised, which demands venous ligaturation and resection as close to the origin in the high mesenteric artery as possible;

At the origin of the high mesenteric artery is the central lymph node station in the right colon drainage close to the aorta; and as a result, it cannot be resected. The oncological feature of the right hemicolectomy is somehow limited.

SEGMENTARY TRANSVERSE COLECTOMY: removal of a portion from the transverse colon, centered by the tumor and achieving the oncological safety edges (at least 5 cm.) on both sides of the lesion. A resection in block is made for the afferent epiploon. Digestive continuity is resumed by termino-terminal colo-colonic anastomosis(Fig 13) which involves the mobilization of the splenic and hepatic angles or if it is not possible for both of then,at least one of them.

Radical surgeries for transverse colon tumors are usually considered to be either the right or the left hemicolectomy, segmental colectomy is usually reserved to patients whose associated pathological history or their general condition makes them to not be able to undergo a complex surgery.

LEFT HEMICOLECTOMY: is for the territory irrigated by the low mesenteric artery ligatured and resected at its origin, together with the central lymph node station of the left colon.This colectomy is considered radical from the oncological point of view. There will be resected: the splenic angle, the descending and partially the sigmoid and also the distal portion of the transverse. The low mesenteric vein is ligatured to the lower edge of the corporeo-caudal junction of the pancreas and Riolan's arcade), i.e., the anastomosis between the ascending branch of the left colic and the left branch of the medium colic) is intercepted at the level of proximal transverse section.

The distal section is made at the sigmoid level and the continuity is resumed by colo-sigmoido anastomosis. In accordance with the tumor location closer to the proximal (splenic angle) or distal (colosigmoid junction) outer edge, the resection limits may be to the proximal – colosigmoid junction – or progress to the distal – rectosigmoid junction.

SEGMENTAL COLECTOMY of the sigmoid: is done for tumors located on the large bowel segment resected after sigmoid arteries cutting, the operation ending by colorectal anastomosis whose irrigation is provided by the descending branch of the left colic artery and the low rectal artery. After doing a resection within the oncological limits, the length of the sigmoid loop usually allows an anastomosis without tension. Sometimes to do this mobilization of the splenic angle is necessary. [23]

EXTENDED COLECTOMY: involve raising as a block the colon segment with the proximal organs invaded by the tumor. For the right colon tumors ,colectomy can be associated with right with cephalic duodenum pancreatectomy or even nephrectomy.

Transverse colon tumors sometimes need association with corporeo-caudal- pancreatectomy or gastric resection. The splenic angle of the colon drains in the spleen hilum and retropancreatically and this might require resection of the spleen and the pancreas tail adding the left hemicolectomy segment. Sometimes left nephrectomy is necessarily done. Hysterectomy, partial or total cistectomy, left annexectomy, enterectomy or limited anterolateral abdominal wall resections are performed when the sigmoid tumors invade the uterus,the abdominal wall ,thin loops,left annex.

TOTAL COLECTOMY: is usually recommended in familial polyposis, when the whole colic frame is populated by adenomatous polyps with potential malignization .Another recommendation is for synchronal multiple cancers, where the location imposes to raise the whole colon to achieve oncological safety.

THE ATTITUDE IN THE EMERGENCIES RELATED TO COLON NEOPLASMS

In case of obstruction, the colon wall is having an increased pressure and develops alteration of the parietal circulation, then the anastomosis is impossible. For this kind of situation, after the tumor from the colon is removed, it is advisable that the operation ends with either a temporary terminal ileostoma in the case of the right colon or by left ileal pouch in the case of the left colon (Hartman's operation); the digestive continuity will be restored later.

Decompression cecostomy (until the normal state has been recovered)is done when there is an obstructive tumor of the ascending colon, , associated with an altered condition of the patient.

The septic environment of the intraperitoneal exposes the anastomosis to the risk of disunion in colic perforations. This recommends avoiding anastomosis in such situations: it is preferable to performn Hartman's type operations, or elevate to skin-level in "double-barreled shotgun" the colic ends resulting after colostomy.

MECHANICAL SUTURES: The fragility and the usual fistulization tendency of colon anastomosis that is done manually made surgeons to use staplers more often. Mechanical suture devices – staplers – perform faster, user-friendly and safer anastomosis. A limitation is the cost of mechanical suture. Comparing to the cost of postoperative fistula treatment, mechanical suture becomes competitive.

There are 3 surgical stapler types:

the TA linear stapler

GIA stapler which cuts the colon slice by means of an incorporated cutter, along with the linear application of 2 rows of clips meant to perform anastomosis

the EEA or CEEA circular stapler, which lays the two rows of staples circularly and concentrically while cutting the colon tissue.

Staplers are available both in the variant for the laparoscopic and also for the open surgery :

Mechanical termino-terminal or termino-lateral anastomosis can be done by EEA staplers,

Latero-lateral ones by GIA staplers,

Stitching the ends resulting after resection by the TA linear stapler.

LAPAROSCOPIC SURGERY The whole variety of colon cancer surgery can be performed laparoscopically .The surgical principles are the same as in open surgery. Anastomosis is done either extracorporeally by limited celiotomies or intracorporeally, by laparoscopic staplers,. The benefits are those of laparoscopic surgery in general: reduced postoperative pain, , short hospitalization, the absence of parietal complications.[23]

POSTOPERATIVE COMPLICATIONS: can be classified into systemic complications and surgical complications .

Surgical complications are relatively frequent, taking into account the less resistant structure of the colic wall as to other digestive segments as well as the hyperseptic character of the intralumenal content at this level.

The anastomotic fistula is the main complication in point of gravity. It occurs on the neoplasic disorder background and sometimes is associated with other conditions ( kidney insufficiency, diabetes, hepatic insufficiency) which affects the colic wall trophicity, to which a series of unfavorable circumstances to anastomosis are added: anastomosis in tension, ischemiant suture, insufficient vascularization.

A situation of reintervention comes when there is a rupture of anastomosis that results in colon contents flowing into the peritoneum. It is done a washout of the peritoneal cavity and deviation of transit to the exterior by a cutaneous stoma. Prevention of anastomotic dehiscence is done by observing the optimal conditions of anastomosis performance , redressing anemia, combating intraperitoneal sepsis, maintaining proteinemy within the normal limits postoperatively, resuming the normal bowel transit approx. 72 hrs postoperatively.

Usually a consequence of a fistula, postoperative peritonitis can also occur after intraoperative peritoneum contamination with fecaloid content. If it is once declared,purulent peritonitis favors the anastomotic fistula occurrence which will alter the patient's condition. The treatment consists in administration of large-spectrum antibiotics and peritoneal tropism, of ertapenem or imipenem, washout and surgical drainage of the peritoneal cavity, alongside with fistula solving.

Other surgical complications are: postoperative hemorrhage, prolonged postoperative ileum,wound suppuration, stomitis – inflammatory stenosis of the mouth.

POSTOPERATORY OBSERVATION: its reason is to have a fast discovery of relapses and metastases, as also to detect possible adenomatous polyps that are susceptible to malignization. The patients that had at the moment of operation a T3 or T4 tumor or positive adenopaties N1-N3 are most prone to neoplasic recurrences .Checkups, annual during the first 3 years, then every 3 years, must include :

physical examination,

an abdominal echography,

a CT scan,

carcinoembryonic antigen dosage (significantly increased in case of relapse or metastasis),

colonoscopy

PALLEATIVE SURGERY: it is used for the advanced stages in which the tumor cannot be resected, or when there are many metastases, or when the patient's fragile condition allows only minimal surgery to be done. The main priority in these kind of situations is given to restoring bowel transit and evacuation, which is carried out by tumor resection and anastomosis. In the case of bleeding tumors, all efforts must be made to respect the latter even if the operation is not oncologically recommended as radical. In situations when the tumor resection is impossible, internal derivation will be performed. The most frequently used methods of tumoral by-pass are those in which a sigmoid-transverse anastomosis is performed in the left colon tumors or in which the ileum is latero-laterally anastomosed to the transverse colon (in ceco-ascending colon cancers). There are also other situations when it comes to using a transparietal bowel transit deviation, achieving a cutaneous stoma proximal to the tumor: on the sigmoid-left ileo-anal pouch ,on the transverse – Bergeret subangulo-colic anus or on the ileum – an ileostoma.

PALLEATIVE COLONOSCOPIC TREATMENT: is an alternative to palliative surgery in case of stenosing colon cancers, thereby avoiding definitive colostomy.(Figure 14)

There should be known that these procedures have temporary and limited efficiency. The main types of palliative interventions which can be made colonoscopically are:

– Partial tumor resection (Debulking): is recommended when there are vegetant tumors, protruding in the lumen, obstructing transit or bleeding ; the tumoral mass reduction can be made by: by the Argon plasma clotting device or by simple clectroclotting or by Nd-YAG (neodynum – yttrium-aluminum-garnet) laser.

– Transtumoral replacement of metal self-expandable prosthetics (Stenting): usually used in case of obstructions produced by infiltrating tumors. The radiological monitoring is used and must be preceded by visualization of the stenosis trajectory by injecting contrast agents. The main disadvantage of transtumoral stenting are: stent migration and re-stenosis .

– Hemostasis achievement in cases of bleeding at the tumors' level: is managed using by photoclotting, electroclotting, Argon-plasma laser or mechanical methods (emplacing hemoclamps).

THE TREATMENT OF METASTASES:

Lung metastases are resected to the extent at which the survival of the patient is kept out of danger.

If there are hepatic metastases(limited in number), they are surgically resected:separately (when they are situated both in the right liver lobe and in the left one), or removed in block using hepatectomy (when the lesions are grouped in a limited hepatic territory).

The alternative solutions to the classical resection of hepatic metastases are:

mono-or bipolar electroclotting;

administration of chemotherapy(intra-arterial), via catheter surgically emplaced in the hepatic artery system (for multiple hepatic metastases).

freezing metastasis tissue with liquid azoth (cryosurgery), or by: radiofrequency, microwaves metastasis nodes softening by afferent circulation embolization;

Ovary metastases are treated by annexectomy.

Peritonectomy is used in certain situations when there are peritoneal metastasis on limited surface. In case of generally extended peritoneal metastases – the peritoneal carcinomatosis – besides the systemic chemotherapy treatment, there was also chemotherapy administration via intraperitoneal instillation.[23]

ADJUVANT TREATMENT For the colon neoplasm is restricted to chemotherapy. Trying to use the radiotherapy brought a lot of comorbidities (radic enteritis). Patients may receive chemotherapy as an injection into a vein or as a pill that can be taken by mouth. Some drugs are given continuously over several days; some are given several times a week. Adjuvant chemotherapy for colon cancer usually includes a drug called fluorouracil (5-FU). Leucovorin (Wellcovorin), irinotecan (Camptosar), and oxaliplatin (Eloxatin) may be given in addition to 5-FU. Most adjuvant chemotherapy treatment schedules last for about six to eight months.