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Microscopic Colitis

Microscopic colitis is a disease that causes chronic, watery diarrhea. Even though there is inflammation, this is not visible to the eye during a colonoscopy. The disease is diagnosed only when biopsies are examined by a pathologist under the microscope (hence the term “microscopic colitis”).

Microscopic colitis may cause abdominal discomfort and pain, but these symptoms are not as serious as in other forms of inflammatory bowel disease (IBD).  Microscopic colitis does not lead to rectal bleeding or colon cancer. However, with severe diarrhea, patients may develop dehydration and electrolyte abnormalities (for example, low potassium levels).

There are two types of microscopic colitis. Symptoms and treatment are similar:

  • Lymphocytic colitis: white blood cells accumulate in the lining of the colon;
  • Collagenous colitis: a thick band of collagen develops under the lining of the colon. The typical patient with collagenous colitis is a middle-aged woman in her sixth decade with otherwise good health (female-to-male ratio up to 15:1).


The root causes of microscopic colitis are unknown. Current research suggests that the following factors may contribute:

  • Abnormal collagen metabolism;
  • Some medications (such as aspirin, NSAIDs and lansoprazole);
  • Bacterial toxins;
  • Bile acid malabsorption.


The symptoms of microscopic colitis sometimes go away without treatment. In some patients, symptoms may occur periodically and at different levels of intensity. Symptoms can include:

  • Chronic watery diarrhea;
  • Abdominal pain or cramps;
  • Unexplained weight loss;
  • Nausea.


The gastroenterologist first performs a thorough history and physical examination. Tests include the following:

  • Blood and stool tests to rule out other conditions, such as infection;
  • Colonoscopy with biopsies to make a definitive diagnosis.


Diet changes (such as avoidance of caffeine and alcohol) can help control diarrhea. Eliminating a drug suspected as the cause of the condition may lead to resolution of symptoms.

Medications may be necessary:

  • Anti-diarrheal medications;
  • Anti-inflammatory medications, such mesalamine drugs, steroids, bile acid binders, and bismuth subsalicylate;
  • Medications (such azathioprine) that suppress the immune system to help reduce inflammation in the colon.
Surgery may be necessary when all medical therapies fail, but this is extremely rare.

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