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Microscopic Colitis (Lymphocytic Colitis and Collagenous Colitis)

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What is colitis?

Colitis means inflammation of the colon. The colon, also known as the large intestine or large bowel, constitutes the last part of the digestive tract. The colon is a long, muscular tube that receives digested food from the small intestine. It removes water from the undigested food, stores the undigested food, and then eliminates it from the body through bowel movements. The rectum is the last part of the colon adjacent to the anus. The common symptoms of colitis include:

There are many different types of colitis with different causes. Some examples of colitis include:

Infectious, radiation, ischemic, ulcerative, and Crohn's colitis all have visible abnormalities of the inner lining of the colon. These abnormalities include edema (swelling of the lining), redness, bleeding from the lining with gentle rubbing (friability), and ulcers. These abnormalities can be seen during colonoscopy (examination of the entire colon using a long flexible viewing tube) or flexible sigmoidoscopy (examination of the rectum and the sigmoid colon - the segment of the colon closest to the rectum).

Edema and inflammation of the colon's lining interferes with the absorption of water from the undigested food, and the unabsorbed water exits the rectum as diarrhea. Pus and fluid also are secreted into the colon and add to the diarrhea. The redness, bleeding from the lining with gentle rubbing (friability), and ulcerations in the lining of the colon contribute to the rectal bleeding.

Picture of Large Intestine (Colon) Anatomy
Picture of Large Intestine (Colon) Anatomy

Medically Reviewed by a Doctor on 8/8/2016


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