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GIT large bowel

الكلية كلية طب الاسنان     القسم  العلوم الاساسية     المرحلة 3
أستاذ المادة علي زكي ناجي الاسدي       25/06/2019 10:07:19
General pathology
2-Ulcerative colitis
it is more common among whites than among blacks, women are affected more than men.
The onset of disease peaks between the ages of 20 and 25 years.
is an ulcero-inflammatory disease limited to the colon and affecting only the mucosa and submucosa .
In contrast to Crohn disease, ulcerative colitis extends in a continuous fashion proximally from the rectum.
Well-formed granulomas are absent.
Gross appearance:
Ulcerative colitis involves the rectum and extends proximally in a retrograde fashion to involve the entire colon (pancolitis) in the more severe case.
In the course of colonic involvement with ulcerative colitis, the mucosa may exhibit slight reddening and granularity with friability and easy bleeding.
The lesion limited to the mucosa and lead to ulcers formations with pseudopolyps.
Microscopical appearance:
Neutrophil infiltration of the epithelial layer may produce collections of neutrophils in crypt lumens (crypt abscesses).
Decrease number of goblet cells.
Mucosal ulcerations.
In contrast to crohn, no granuloma formation.
Clinical Feature:-
Ulcerative colitis typically presents as a relapsing disorder marked by attacks of bloody mucoid diarrhea that may persist for days, weeks, or months, then subside, only to recur after an asymptomatic interval of months to years or even decades.
Increased risk of developing colorectal carcinoma in 20 – 30 folds.

TUMORS OF THE COLON AND RECTUM
A polyp is a tumorous mass that protrudes into the lumen of the gut.
These are of two types:
1- Hyperplastic polyp: formed as the result of abnormal mucosal maturation, inflammation, or architecture. These are small, arise at any age. They often are multiple, and more than half are found in the rectosigmoid.
Histologically, they are composed of well-formed glands and crypts lined by non-neoplastic epithelial cells, with mature goblet cells.
These polyps are non-neoplastic and do not have the ability to change to malignant tumors.
2- Epithelial polyps (adenomas): Adenomatous polyps are benign tumors that range from small, often pedunculated lesions to large neoplasms that are usually sessile. The prevalence of colonic adenomas is about 20 to 30% before age 40, rising to 40 to 50% after age 60. Men and women are affected equally.
They have the ability for malignant transformation.
Adenomatous polyps are of three subtypes:
1- Tubular adenomas: Tubular glands
2- Villous adenomas: Villous projections
3- Tubulovillous adenoma: A mixture of the previous two
Colorectal Carcinoma
Epidemiology, Etiology, and Pathogenesis.
The peak incidence for colorectal carcinoma is 60 to 80 years. When colorectal carcinoma is found in a young person, preexisting ulcerative colitis or one of the polyposis syndromes must be suspected. Colorectal carcinoma has a worldwide distribution, with the highest death rates in the United States and Eastern European countries. Environmental factors, particularly dietary practices, are important in these geographic contrasts, obesity and physical inactivity as risk factors for colon cancer. The dietary factors receiving the most attention as predisposing to a higher incidence of cancer are
(1) excess energy intake relative to requirements.
(2) a low content of un absorbable vegetable fiber.
(3) a corresponding high content of refined carbohydrates.
(4) intake of red meat.
(5) decreased intake of protective micronutrients and antioxidants.
MORPHOLOGY.
Site: cecum and sigmoid are the most common sites.
Tumors in the proximal colon tend to grow as polypoid, exophytic masses, and obstruction is uncommon. When carcinomas in the distal colon are discovered, they tend to be annular, encircling lesions and presenting clinically as intestinal obstruction.
microscopic characteristics of right-sided and left-sided colonic adenocarcinomas are similar. Differentiation may range from tall, columnar cells resembling their counterparts in adenomatous lesions to undifferentiated, frankly anaplastic masses.
Clinical Features.
Colorectal cancers remain asymptomatic for years; symptoms develop slowely and frequently have been present for months, sometimes years, before diagnosis. Cecal and right colonic cancers are most often called to clinical attention by the appearance of fatigue, weakness, and iron deficiency anemia. These bulky lesions bleed and may be discovered at an early stage, provided that the colon is examined thoroughly radiographically and during colonoscopy. Left-sided lesions come to attention by producing occult bleeding, changes in bowel habit, or left-lower-quadrant discomfort. It is a clinical maxim that iron deficiency anemia in an older man means gastrointestinal cancer until proven otherwise.
All colorectal tumors spread by direct extension into adjacent structures and by metastasis through the lymphatics and blood vessels. In order of preference, the favored sites of metastatic spread are the regional lymph nodes, liver, lungs, and bones. In general, the disease has spread beyond the range of curative surgery in 25 to 30% of patients.
Stage of the tumor is very important prognostic parameter as in any other tumors, there are different staging system for colorectal carcinoma, but still the Duke staging system is most popular one, in which:
Dukes stage A = Tumor affect mucosal layer only.
Dukes stage B1 = Tumor invade the wall with negative regional LNs spread.
Dukes stage B2 = Tumor invade through full wall thickness but negative regional LNs spread.
Dukes stage C1 = Tumor invade the wall with Positive regional LNs spread.
Dukes stage C2 = Tumor invade through full wall thickness with positive regional LNs spread.


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