Microscopic colitis got its name because a microscope must be used to look at tissue samples to make the diagnosis. This syndrome includes two disorders—collagenous colitis and lymphocytic colitis. These two kinds of bowel inflammation affect the colon (large intestine, or bowel). They aren’t related to Crohn’s disease or ulcerative colitis.
More women than men have collagenous colitis; lymphocytic colitis affects men and women equally. People are usually first diagnosed in their 50s or 60s.
The cause is unknown. However, bacteria and their toxins, viruses, and nonsteroidal antiinflammatory drugs (NSAIDs) or other drugs may damage the bowel lining. NSAIDs include aspirin, ibuprofen, and naproxen. An autoimmune response may cause the colitis. This means that the body’s own immune (infection-fighting) system does not recognize cells as belonging to one’s body and destroys them. The disorder can run in families.
The main symptom is chronic watery, nonbloody diarrhea. It often starts quite suddenly. The diarrhea may be constant or come and go. Other symptoms are pain, cramps, or bloating in the abdomen (belly); weight loss; nausea; fecal incontinence; and dehydration.
The health care provider may suspect microscopic diarrhea based on the medical history and physical exam. A colonoscopy will be done. For a colonoscopy, the doctor puts a tube through the large bowel. The tube has a lighted end and camera so that the health care provider can see inside the colon. Specific biopsy findings are needed to confirm the diagnosis. For a biopsy, the doctor takes small pieces of bowel tissue for study with a microscope. In collagenous colitis, the bowel lining has a thickened layer of connective tissue (collagen). In lymphocytic colitis, tissue pieces show inflammation with many white blood cells (lymphocytes) in the bowel lining, but with normal collagen.
Lifestyle changes to stop diarrhea are usually tried first. The amount of fat in the diet is reduced, foods that contain caffeine or lactose are avoided, and NSAIDs are stopped. If these changes aren’t enough, drugs are tried. Medicines such as bismuth subsalicylate (Pepto-Bismol), loperamide (Imodium), or the combination diphenoxylate and atropine (Lomotil) may help the diarrhea. Bulking agents (psyllium, methylcellulose) may also help. Antiinflammatory medicines, such as mesalamine, sulfasalazine, and steroids including budesonide, reduce inflammation.
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