Microscopic colitis takes two forms: collagenous colitis and lymphocytic colitis. Collagenous colitis and lymphocytic colitis are two types of bowel inflammation that affect the colon (large intestine). They are not related to Crohns disease or ulcerative colitis, which are more severe forms of inflammatory bowel disease (IBD).
Collagenous colitis and lymphocytic colitis are referred to as microscopic colitis because colonoscopy usually shows no signs of inflammation on the surface of the colon. Instead, tissue samples from the colon must be examined under a microscope to make the diagnosis.
No precise cause has been found for collagenous colitis or lymphocytic colitis. Possible causes of damage to the lining of the colon are bacteria and their toxins, viruses, or nonsteroidal anti-inflammatory drugs (NSAIDs). Some researchers have suggested that collagenous colitis and lymphocytic colitis result from an autoimmune response, which means that the body’s immune system destroys cells for no known reason.
The symptoms of collagenous colitis and lymphocytic colitis are similar–chronic watery, nonbloody diarrhea. The diarrhea may be continuous or episodic. Abdominal pain or cramps may also be present.
The diagnosis of collagenous colitis or lymphocytic colitis is made after tissue samples taken during colonoscopy or flexible sigmoidoscopy are examined under a microscope. Collagenous colitis is characterized by a larger-than-normal band of protein called collagen inside the lining of the colon. The thickness of the band varies, so multiple tissue samples from different areas of the colon may need to be examined. In lymphocytic colitis, tissue samples show inflammation with white blood cells known as lymphocytes between the cells that line the colon, and in contrast to collagenous colitis, there is no abnormality of the collagen.
People with collagenous colitis are most often diagnosed in their 50s, although some cases have been reported in adults younger than 45 years and in children aged 5 to 12. It is diagnosed more frequently in women than men.
People with lymphocytic colitis are also generally diagnosed in their 50s. Both men and women are equally affected.
Treatment for collagenous colitis and lymphocytic colitis varies depending on the symptoms and severity of the cases. The diseases have been known to resolve spontaneously, but most patients have recurrent symptoms.
Lifestyle changes aimed at improving diarrhea are usually tried first. Recommended changes include reducing the amount of fat in the diet, eliminating foods that contain caffeine or lactose, and not using NSAIDs.
If lifestyle changes alone are not enough, medications are often used to control the symptoms of collagenous colitis and lymphocytic colitis.
• Antidiarrheal medications such as bismuth subsalicylate and bulking agents reduce diarrhea.
• Anti-inflammatory medications, such as mesalamine, sulfasalazine, and steroids including budesonide, reduce inflammation.
• Immunosuppressive agents, which reduce the autoimmune response, are rarely needed.
• For very extreme cases of collagenous colitis and lymphocytic colitis, bypass of the colon or surgery to remove all or part of the colon has been done in a few patients. This is rarely recommended. Collagenous colitis and lymphocytic colitis do not increase the risk of colon cancer.