Background: It has been suggested that appendectomy may protect against ulcerative colitis (UC). However, the incidences of appendectomy and UC in developed countries have diverged over the last 50 years, possibly as a consequence of environmental factors.
Aim: To determine whether the incidence of appendectomy is lower in patients with UC than in the general population.
Methods: Patients with UC (153), their relatives (116) and members of the general population (306) that had been matched for age, sex and educational status were studied.
Results: Six per cent of UC patients had undergone appendectomy. The corresponding figure for non-family controls was 20% (P < 0.0001; OR = 0.27; 95% CI = 0.15-0.45). The rate of appendectomy within families (cases plus siblings) was 17/269 (6.3%) and was similar to that for UC patients alone(P < 0.001).
Conclusions: A negative association between appendectomy and UC exists in our patients with UC. In addition, the appendectomy rate in families of UC patients was lower than that in the general population, possibly implying that common environmental and genetic factors could play an important role in the divergent incidences of appendicitis and UC over the last 50 years.