Your doctor will take a careful history of all your symptoms as some can be similar to other conditions such as Irritable Bowel Syndrome (IBS).

Colonoscopy with biopsy

In Microscopic Colitis, changes in the gut can only be seen under the microscope. So, to diagnose the condition a small tissue sample (biopsy) is taken from the colon when you have a colonoscopy. This is then looked at under a microscope.   

In a colonoscopy, a long flexible tube (about the thickness of your little finger) with a bright light and camera at its tip is inserted through the anus, allowing the specialist to examine the lining of the colon. During the investigation, the specialist will painlessly remove small pieces of tissue from the lining of the colon, to examine in the laboratory under a microscope.

The doctor won’t be able to see any visible signs of inflammation when they look at your colon and rectum. This is different from Crohn’s or Ulcerative Colitis when inflammation or ulcers can be seen.

Other tests you may have 

You may have a test for bile acid malabsorption. This is usually carried out in the Nuclear Medicine outpatient department of the hospital. You’ll be given a small capsule of a synthetic bile salts to swallow which contains a small amount of harmless radioactive material known as SeHCAT. You’ll then have a scan and another one a week later. These will measure the absorption of the radioactive bile salts.

Delay in getting a diagnosis

It may take some time to get a diagnosis of Microscopic Colitis, and this can be frustrating.This may be because:

• A poo test (faecal calprotectin) isn’t usually helpful – this finds evidence of inflammation in the gut, but with Microscopic Colitis levels are often quite low.
• Your colon and rectum will look normal at colonoscopy - it is vital to take biopsies to find Microscopic Colitis. 
• Symptoms may be similar to other conditions such as Irritable Bowel Syndrome (IBS) or coeliac disease which doctors may be more familiar with.