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Complications of Crohn's disease and ulcerative colitis

2-minute read

The most common complications of these diseases are to do with the gut. A small number of people with Crohn's disease or ulcerative colitis can develop complications due to inflammation in other parts of the body, such as the liver, the skin, the joints and the eyes.

Prevention of complications include regular monitoring, including colonoscopies. A doctor who specialises in the gut, called a gastroenterologist, is often involved in the management of these conditions. Medications, including steroids and drugs designed to prevent inflammation, and also occasionally surgery, are required to help prevent complications.

Osteoporosis (thinning of the bones) may also sometimes develop as a side effect of long-term corticosteroid use.

Other complications specific to each condition are described below.


Cases of marked inflammation can cause:

  • abdominal pain
  • diarrhoea, often with blood and mucous
  • weight loss
  • nutritional deficiencies
  • heavy bleeding due to deep ulcers
  • perforation (rupture) of the bowel
  • problems with the bile ducts, affecting the liver
  • fulminant colitis/toxic megacolon, where the bowel stops working

In the long-term, colitis is associated with an increased risk of developing bowel cancer. After 10 years the risk of bowel cancer is 1 in 50, and after 20 years it increases to 1 in 12. This risk can be decreased by maintaining a healthy diet, exercising and avoiding alcohol and smoking. Regular colonoscopy is also usually recommended to monitor the bowel.

Crohn's disease

Crohn's disease can cause blocking or narrowing of the bowel (stricture) which causes the bowel contents to get stuck. When this happens symptoms include increasing abdominal pain and cramping, vomiting, bloating and a feeling of fullness in the abdomen. This is a medical emergency that requires a trip to hospital.

If you suspect that you are having a life-threating medical emergency, dial triple zero (000) immediately.

Crohn's disease can also cause complications to develop anywhere in the gut, from the mouth to the anus. Complications around the anus include:

  • abscesses (boils)
  • flaps of thickened skin
  • fissures (ulcerated tears or cracks in the lining of the anal canal)

Crohn's disease may also cause fistulas, which are abnormal tunnels that connect loops of intestine together or to other organs. They usually develop in areas of severe scarring and ulceration. A large fistula may require surgery to flush out any contents and promote healing.

Crohn's disease can also cause diarrhea sometimes with blood and mucous, abdominal pain, weight loss and nutritional deficiencies.

Last reviewed: January 2018

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