What is microscopic colitis?

Microscopic colitis is an inflammatory bowel disease (IBD) that affects the colon and the rectum. It is called microscopic colitis because it requires a microscope to diagnose it and differentiate between the two types  – collagenous colitis and lymphocytic colitis. To diagnose the condition, a person has a colonoscopy during which a biopsy is taken and the tissue is then looked at under a microscope. It is not known what causes this condition but it happens when the body’s immune system attacks healthy cells in the colon, causing inflammation of the lining of the colon.

Microscopic colitis is more often diagnosed in people over the age of 50, particularly females and those who have an autoimmune condition. Certain medications, as well as smoking, can also increase the likelihood of having microscopic colitis.

Symptoms of microscopic colitis

The symptoms of microscopic colitis are:

  • diarrhoea, which can be frequent, urgent and may also include episodes of incontinence
  • abdominal pain
  • wind
  • bloating
  • tiredness or fatigue
  • weight loss
  • joint pain

What are the two types of microscopic colitis?

The two types of microscopic colitis are collagenous colitis and lymphocytic colitis.

  • Collagenous colitis is when the inner lining of the colon has a thicker layer of collagen than usual.
  • Lymphocytic colitis is when the inner lining has more white blood cells than usual.

Both of these conditions can cause the colon to absorb less liquid from the waste in the body, leading to the buildup of fluid and subsequently diarrhoea. Although they look different under a microscope, they have the same symptoms and treatments.


Medication can help to relieve the symptoms of microscopic colitis. This includes loperamide to help with diarrhoea and steroids to reduce inflammation. Lifestyle and dietary changes may also help reduce diarrhoea.

How is microscopic colitis different from ulcerative colitis?

While both microscopic colitis and ulcerative colitis can cause inflammation of the colon, ulcerative colitis can be seen during a colonoscopy and microscopic colitis is typically only seen under a microscope. Ulcerative colitis can also present with blood in your poo and can increase a person’s risk of bowel cancer, while neither of these are true for microscopic colitis.