LAUSR

Dear Editor: A potential protective effect of appendectomy toward UCwas first reported in a case control study of 174 patients with ulcerative colitis (UC) and 161 controls from an orthopedic ward 26 years ago [1]. This association has been confirmed by recent meta-analyses including more than 15,000 cases [2] and has been intensively debated even in the International Journal of Colorectal Disease [3]. Whereas case control studies are often matched for age and sex, they rarely control for familial risk of UC and environmental factors [4]. In a specific approach to control these potential confounders, we performed a matched case control study including adult 1030 patients with inflammatory bowel disease (IBD) and their 1030 full siblings without IBD, who were asked to fill out questionnaire on environmental factors in childhood and early adulthood [5]. UC patients (n = 430) and their siblings as controls (n = 430) were eligible, if they had grown up in the same household and were still in contact with the same caregiver in order to verify answers in cases of doubt. We now used this data set to analyze the reported frequencies of surgical removals of mucosa-associated lymphoid tissues (appendectomy, adenoidectomy, and tonsillectomy). Analysis of our data shows that patients with UC less often underwent appendectomy before the age of 15 years as compared to their siblings (0.5% versus 5.3%; P = 0.00002) as also shown in Table 1. This protective effect was not observed for adenoidectomy and tonsillectomy and more important, in patients with Crohn’s disease in line with the literature [2]. Despite the limitations of a retrospective questionnaire analysis, the given uncertainty of appendectomy indication, and histologic results, our data strongly support the large effect size of appendectomy on the incidence of UC in a design controlling for genetic and environmental risk factors. It is tempting to speculate whether children at genetically high risk for UC may benefit from preventive appendectomy and whether prospective clinical trials will ever answer this question.