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We read with great interest the article by Hallas and colleagues (Gut 2004;53:351–4) investigating the protective role of appendicectomy in reducing hospital admission rates in patients with ulcerative colitis.
The population studied consisted of a cohort of 202 cases who underwent appendicectomy after their first admission for ulcerative colitis. A population of patients affected by ulcerative colitis who had not an appendicectomy was used as a reference cohort. The authors suggested that appendicectomy had no significant beneficial effect on hospital admission rates in patients with ulcerative colitis as no differences were found between the study and the reference cohort in the decline in hospitalisations. Mean age of the study population was 38.6 years and no stratification of data for any age was performed. Several papers1,2 on the supposed protective role of appendicectomy against ulcerative colitis concluded that appendicectomy is associated with a low risk of subsequent ulcerative colitis only for patients who had surgery before the age of 20 years old. Hence we wondered if the results of Hallas et al might be different if the study population were analysed after stratification for patients younger and older than 20 years.
Dr Adani and colleagues pose a very interesting question. Some studies have suggested that appendicectomy only confers a prophylactic effect against ulcerative colitis (UC) if performed before the age of 20 years. Thus it would be conceivable that the therapeutic effect (that is, ability to reduce admissions for those who already have UC) might be confined to this age group also.
Unfortunately, we cannot provide a precise answer to their question. Only 11 subjects in our cohort had their appendicectomy performed before the age of 20 years, which is far too few patients to allow a meaningful analysis. Our lack of very young subjects is probably a selection phenomenon; we required patients to have their onset of UC before their appendicectomy. As it is unlikely that a person would experience both the onset of UC and an appendicectomy (in that order) before the age of 20 years, eligible subjects become very scarce.
If we raise the limit and examine those who had their appendicectomy before the age of 30 years, we can identify 59 index subjects and 236 reference subjects. By a method similar to the main analysis in our article, we find an adjusted incidence rate ratio of 1.20 (95% confidence interval 0.71–2.01), implying that the incidence of hospital admissions is 20% higher than expected after appendicectomy, albeit with very wide confidence intervals that do not rule out a small therapeutic effect.
In conclusion, our data to support the notion that appendicectomy would be useful against UC in young subjects.
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