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Complications of Crohn's diseases and ulcerative colitis

A small number of people with Crohn's diseases or colitis can develop complications due to inflammation in other parts of the body, such as the liver, the skin, the joints and the eyes.

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.


Rare cases of very severe inflammation can cause:

  • heavy bleeding due to deep ulcers
  • perforation (rupture) of the bowel
  • 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. Symptoms include 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 inside and around the anus (back passage). These complications 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.

Sources: Colorectal Surgical Society of Australia and New Zealand (Crohn's disease, Ulcerative colitis), Crohn's and Colitis Australia (What is ulcerative colitis?, What is Crohn's disease?, What is IBD?, Smoking and Crohn's Disease), NHS Choices, UK (Crohn's disease - Complications, Ulcerative colitis - Complications)

Last reviewed: September 2015

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