Last reviewed 01/2018

The aetiology of Ulcerative colitis (UC) is unclear.

It is thought to occur due to the interaction of genetic factors and environmental triggers (1).

It is probably an autoimmune disease caused by an inflammatory response to normal colonic microflora (1).

Several risk factors have been identified:

  • not smoking
    • smoking has a universal protective effect resulting in a decrease in the risk of developing UC (a 40% lower risk) than in non smokers (1,2)
    • but in former smokers the risk of developing UC is approximately 1.7 times more higher than in non smokers (2)
    • it is also associated with a milder course of the disease (1)
  • a family history of inflammatory bowel disease
  • non-selective NSAIDs - can cause exacerbation of UC
  • appendicectomy performed for "true" appendicitis at an early age appears to have some protective effect against developing UC (2)