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Microscopic colitis

Medically reviewed by Last updated on Jan 16, 2024.


Microscopic colitis is swelling and irritation, called inflammation, of the large intestine. This large intestine is also called the colon. Microscopic colitis causes symptoms of watery diarrhea.

The condition gets its name from needing to look at colon tissue under a microscope to diagnose it. The tissue appears typical on exam with a colonoscopy or flexible sigmoidoscopy.

There are two subtypes of microscopic colitis:

Researchers believe collagenous (kuh-LAYJ-uh-nus) colitis and lymphocytic colitis may be forms of the same condition. Symptoms, testing and treatment are the same for both subtypes.

Colon and rectum

The colon is a long tube-like organ in the abdomen. It's the largest part of the large intestine. The colon carries waste to be expelled from the body. The rectum makes up the last several inches of the colon.


Symptoms of microscopic colitis include:

The symptoms of microscopic colitis can come and go. At times, symptoms improve on their own.

When to see a doctor

If you have watery diarrhea that lasts more than a few days, contact your healthcare professional to diagnose and treat your condition.


It's not clear what causes the swelling and irritation, called inflammation, of the colon found in microscopic colitis. Researchers believe that the causes may include:

Risk factors

Risk factors for microscopic colitis include:

Some research studies show a link between using certain medicines that may increase the risk of microscopic colitis. But not all studies agree.

Medicines that may be linked to the condition include:


There are minimal complications for most people once microscopic colitis is successfully treated. The condition does not increase the risk of colon cancer.


A complete medical history, physical exam and testing can help tell whether other conditions, such as celiac disease, may be causing diarrhea. Your healthcare professional also will ask about medicines you take.


To help confirm a diagnosis of microscopic colitis, you may have one or more of the following tests and procedures:

Intestinal tissues often appear typical in microscopic colitis. So a colon tissue sample, called a biopsy, taken during a colonoscopy or flexible sigmoidoscopy is needed to confirm a diagnosis.

In both subtypes of microscopic colitis, cells in colon tissue can be seen under the microscope to make a diagnosis.

Other testing

Besides a colonoscopy or flexible sigmoidoscopy, you may have one or more of these tests to rule out other causes for your symptoms.


During a colonoscopy, the healthcare professional puts a colonoscope into the rectum to check the entire colon.

Sigmoidoscopy exam

During a flexible sigmoidoscopy exam, the healthcare professional puts a sigmoidoscope into the rectum to check the lower colon.


Microscopic colitis may get better on its own. But when symptoms are severe or don't go away, you may need treatment to relieve them. Healthcare professionals most often start with the simplest treatments that are least likely to cause side effects.

Diet and stopping certain medicines

Treatment usually begins with changes to your diet and medicines that may help relieve diarrhea. Your healthcare professional might suggest that you:


If you keep having symptoms, your healthcare professional may suggest:


Very rarely, when the symptoms of microscopic colitis are severe and medicines don't work, your healthcare professional may suggest surgery to remove all or part of your colon.

Lifestyle and home remedies

Changes to your diet may help relieve the diarrhea of microscopic colitis. Try to:

Preparing for an appointment

Here's some information to help you get ready for your appointment.

What you can do

Questions to ask your doctor

Some basic questions to ask your healthcare professional include:

If you do not understand something, don’t hesitate to ask questions.

What to expect from your doctor

Your healthcare professional is likely to ask you:

What you can do in the meantime

You may find some relief from diarrhea by making changes to your diet:

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