Microscopic colitis - what it is and why it matters

Diarrhoea is a really difficult symptom for patients to manage, particularly when it causes urgency of defaecation (the need to get to the toilet immediately). Many causes of diarrhoea are short-lived, like gastrointestinal infections that usually settle quickly. However chronic (long-term) diarrhoea can happen due to a variety of causes. This can have a terrible impact on people’s quality of life, as the urgency and unpredictability of bowel movements can stop people from working, travelling, or enjoying their usual activities.

There are lots of possible causes of persistent diarrhoea, including Crohn’s disease and ulcerative colitis, bowel cancers, coeliac disease, problems with the pancreas, bile acid malabsorption, and certain food intolerances. However, one important cause, which can easily be missed, is a condition called microscopic colitis.

Microscopic colitis usually causes watery diarrhoea, with patients affected often opening their bowels many times a day, with considerable urgency. The condition is more common in women, particularly in their 40s and older, but it can affect any age, and men also. Sometimes it can be related to medications (antiacid medications called PPIs, pain-killers like ibuprofen or diclofenac, and some antidepressants), and sometimes it can be caused by another immune condition, coeliac disease. However frequently it comes on with no clear trigger.

The only way to diagnose the condition is with a colonoscopy, and tiny samples of the lining of the colon called biopsies. During the camera test we often can’t see many changes, but under the microscope we can see an increase in certain white blood cells in the lining of the gut (lymphocytic colitis) or an increase in the collagen layer in the lining (collagenous colitis). This confirms the diagnosis so we can start treatment.

Fortunately most people respond really well to treatment. We use a type of steroid (called budesonide) that rarely causes side effects, and over 90% of people will have a good response to this. We will also remove any triggers of the condition. Unfortunately about half of people will have symptoms in the following year after the first course of medication is stopped, but usually with further budesonide, or a variety of other treatments, we can get people’s symptoms under control, and get their quality of life back.

If you have symptoms of persistent diarrhoea, it is really important to get this checked out, both to rule out worrying conditions like bowel cancer, and so that we can uncover a cause and improve symptoms. Do see your primary care doctor for initial tests, or a gastroenterologist who can appropriately investigate.