Microscopic Colitis

What is microscopic colitis?

Microscopic colitis is a type of inflammation of the large intestine (colon) that causes chronic, watery, non-bloody diarrhea. It gets its name because the lining of the colon appears normal to the naked eye during a colonoscopy, and the diagnosis can only be made by examining biopsies of the colon tissue under a microscope.

There are two main subtypes of microscopic colitis:

• Collagenous colitis: In this form, a thick layer of protein (collagen) develops in the tissue beneath the surface lining of the colon.
• Lymphocytic colitis: In this form, there is an increased number of white blood cells (lymphocytes) within the surface lining of the colon.

While they look different under the microscope, the symptoms and treatment for both subtypes are the same.

What are the symptoms of microscopic colitis?

The hallmark symptom of microscopic colitis is chronic watery diarrhea. The diarrhea is non-bloody and can be persistent or come and go. The frequency can range from a few loose stools to more than 10 watery stools per day.

Other symptoms may include:

• Abdominal cramping or pain
• Urgency to have a bowel movement
• Fecal incontinence
• Nausea
• Weight loss
• Fatigue

What causes microscopic colitis?

The exact cause of microscopic colitis is not known. It is thought to be the result of an abnormal immune response to a trigger in the colon in people who may be genetically predisposed. Several factors are thought to be associated with the condition:

• Medications: A number of medications have been strongly linked to microscopic colitis. The most common culprits include nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen, proton pump inhibitors (PPIs) used for acid reflux, and selective serotonin reuptake inhibitors (SSRIs) used for depression.
• Autoimmune diseases: Microscopic colitis is more common in people who have other autoimmune diseases, such as celiac disease, thyroid disease, rheumatoid arthritis, and type 1 diabetes.
• Infection: It's possible that a previous bacterial or viral infection could trigger the inflammatory response.
• Bile Acid Malabsorption: Some people with microscopic colitis may also have a condition where bile acids are not properly reabsorbed in the small intestine, leading to irritation of the colon and diarrhea.
• Smoking: Cigarette smoking is a known risk factor, particularly for collagenous colitis.

How is microscopic colitis diagnosed?

Because the colon looks normal on a colonoscopy, the diagnosis of microscopic colitis requires biopsies of the colon lining.

• Colonoscopy with Biopsies: A colonoscopy is performed to examine the colon and, importantly, to rule out other causes of chronic diarrhea, such as inflammatory bowel disease (Crohn's disease or ulcerative colitis). During the procedure, the doctor will take multiple small tissue samples (biopsies) from different parts of the colon. These biopsies are then examined by a pathologist under a microscope to look for the characteristic signs of either collagenous or lymphocytic colitis.
• Stool and Blood Tests: These are usually done to rule out infections and other conditions like celiac disease.

How is microscopic colitis treated?

Treatment is focused on reducing the inflammation and controlling the diarrhea.

• Discontinuing Triggering Medications: The first step is often to stop any medications that may be causing the colitis, such as NSAIDs or PPIs, if possible.
• Anti-diarrheal Medications: Medications like loperamide can help manage mild diarrhea.
• Budesonide: This is the most effective and first-line medication for treating microscopic colitis. Budesonide is a type of corticosteroid that is specifically designed to work in the gut with minimal absorption into the rest of the body, which greatly reduces the side effects seen with other steroids like prednisone. It is very effective at inducing remission.
• Bile Acid Binders: For patients who may also have bile acid malabsorption, medications like cholestyramine can be helpful.
• Immunomodulators or Biologic Therapies: For the small number of patients with severe disease that does not respond to budesonide, more powerful immune-suppressing medications may be used.

Self-Care and Diet

While diet does not cause microscopic colitis, some dietary changes may help to manage symptoms.

• Avoid Trigger Foods: Some people find that their diarrhea is worsened by caffeine, alcohol, spicy foods, fatty foods, or dairy (lactose).
• Low-Fiber Diet: During a flare, a low-fiber diet may help to reduce the frequency of bowel movements.
• Smoking Cessation: Since smoking is a risk factor, quitting is strongly recommended.

Is microscopic colitis a form of IBD?
While it is a type of colitis (inflammation of the colon), it is generally considered a separate entity from the classic forms of inflammatory bowel disease (IBD), which are ulcerative colitis and Crohn's disease. Unlike IBD, microscopic colitis does not typically cause visible ulcers, does not increase the risk of colon cancer, and does not usually lead to the need for surgery.

Will I have this condition for the rest of my life?
Microscopic colitis can be a chronic condition with periods of flare-ups and remission. However, a significant number of people experience spontaneous resolution of their symptoms, and many who respond to treatment with budesonide can stop the medication and remain in remission for a long time.

Does microscopic colitis increase my risk of colon cancer?
No. Current evidence does not show an increased risk of developing colorectal cancer in people with microscopic colitis.

• Cannon JA, Kennedy GD. Radiation, Microscopic, and Ischemic Colitis. In: Steele SR, Hull TL, Hyman N, Maykel JA, Read TE, Whitlow CB, eds. The ASCRS Textbook of Colon and Rectal Surgery. 4th ed. Springer; 2022:897-900.
• National Institute of Diabetes and Digestive and Kidney Diseases. Microscopic Colitis. Published June 2021. Accessed October 12, 2025. https://www.niddk.nih.gov/health-information/digestive-diseases/microscopic-colitis
• Mayo Clinic. Microscopic Colitis. Accessed October 12, 2025. https://www.mayoclinic.org/diseases-conditions/microscopic-colitis/symptoms-causes/syc-20351478