Collagenous colitis and lymphocytic colitis are chronic diseases, characterized by watery diarrhea, in which certain kinds of white blood cells infiltrate the lining of the large intestine.

These chronic diseases can affect the entire length of the large intestine, including the sigmoid colon and the rectum, but often in a patchy distribution. The lining of the intestine develops a thicker layer of a type of connective tissue (collagen) or an accumulation of lymphocytes (a certain type of white blood cell).

The cause is unknown, although an overactive immune response to some unidentified triggering factor seems possible. Many people who develop collagenous colitis or lymphocytic colitis have been regular users of nonsteroidal anti-inflammatory drugs (NSAIDs), but these drugs have not been proven to be a cause of the diseases. Unlike Crohn's disease and ulcerative colitis, collagenous colitis and lymphocytic colitis do not increase the risk of colon cancer.

Collagenous colitis develops primarily in middle-aged or older women, whereas lymphocytic colitis may develop in younger people and occurs in both sexes equally.

Symptoms and Diagnosis

In addition to nonbloody, watery diarrhea, people with collagenous colitis or lymphocytic colitis often experience crampy abdominal pain, nausea, abdominal expansion (distention), and weight loss. Fasting for a few days often leads to a decrease in the frequency and amount of diarrhea. Diarrhea and other symptoms often fluctuate, with periods of worsening symptoms and periods of improvement or complete resolution.

A doctor considers the diagnosis of collagenous colitis or lymphocytic colitis when a person has persistent watery diarrhea and when tests do not reveal another cause. The diseases are diagnosed by microscopic examination of several samples of tissue taken from the lining of the large intestine obtained during colonoscopy (examination of the large intestine with a flexible viewing tube).

Treatment

Antidiarrheal drugs, such as drugs with anticholinergic effects (for example, many antihistamines and some antidepressants) or small doses of loperamideSome Trade Names
IMODIUM
or diphenoxylate, are effective for many people with these diseases. Anti-inflammatory drugs such as bismuth subsalicylateSome Trade Names
PEPTO-BISMOL
, sulfasalazineSome Trade Names
AZULFIDINE
, and mesalamineSome Trade Names
ASACOL CANASA
are sometimes effective as well. BudesonideSome Trade Names
RHINOCORT
, a newer corticosteroid with fewer side effects, may be very helpful. Otherwise, cholestyramineSome Trade Names
QUESTRAN
, a drug that binds bile acids, or antibiotics may be useful. Corticosteroids (such as prednisone) also work well but, because of their serious possible side effects, are usually reserved for people who do not respond to other drug treatment.

Last full review/revision August 2006 by David B. Sachar, MD; Aaron E. Walfish, MD