Aetiology

The aetiology of Ulcerative colitis (UC) is unclear but is thought to occur due to the interaction of genetic factors and environmental triggers. It is probably an autoimmune disease caused by an inflammatory response to normal colonic microflora (1) and among patients with UC, 10% to 20% will have a family history of inflammatory bowel disease. (2)

Several risk factors have been identified: (3)

• 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
  • but in former smokers the risk of developing UC is approximately 1.7 times more higher than in non smokers
  • it is also associated with a milder course of the disease
• 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

Reference:

1. Sartor RB. Mechanisms of disease: pathogenesis of Crohn's disease and ulcerative colitis. Nat Clin Pract Gastroenterol Hepatol. 2006 Jul;3(7):390-407.
2. Childers RE, Eluri S, Vazquez C, et al. Family history of inflammatory bowel disease among patients with ulcerative colitis: a systematic review and meta-analysis. J Crohns Colitis. 2014 Nov;8(11):1480-97.
3. Harbord M, Eliakim R, Bettenworth D, et al. Third European evidence-based consensus on diagnosis and management of ulcerative colitis. Part 2: current management. J Crohns Colitis. 2017 Jul 1;11(7):769-84.