Microscopic colitis is a type of inflammatory bowel (colon) disease that causes persistent watery diarrhea. In order to identify the disorder, bowel tissue must be viewed under a microscope, as the tissue appears to be normal when examined during a colonoscopy or sigmoidoscopy.

There are three subtypes of microscopic colitis:

• Collagenous colitis: a layer of collagen grows in the bowel tissue
• Lymphocytic colitis: lymphocytes (white blood cells) multiply in bowel tissue
• Incomplete microscopic colitis: both features of collagenous and lymphocytic colitis are exhibited

Regardless of subtype, symptoms, testing and treatment remain the same.

Symptoms

Signs and symptoms include:

• Chronic watery diarrhea
• Cramps, bloating or abdominal pain
• Nausea
• Weight loss
• Dehydration
• Fecal incontinence

Symptoms may come and go, and periodically resolve on their own.

Should You See a Doctor?

If symptoms last more than a few days, particularly watery diarrhea, contact your doctor so they can assess and, if needed, treat your condition.

Causes

It’s unclear what causes bowel inflammation. Possibilities include:

• Autoimmune diseases, such as celiac disease and rheumatoid arthritis, which attack the body’s healthy tissues
• Viruses that produce inflammation
• Bacteria that generate inflammation in the colon’s lining
• Medications that irritate the colon lining