Acute appendicitis for Christmas? The silver lining of reduced risk of ulcerative colitis

With Christmas fast approaching and new papers coming through all the time it’s time for another blog. For the last blog in 2022 I’m going to treat myself and discuss a paper on the incidence of ulcerative colitis following acute appendicitis and dive into some of the surrounding literature on appendicectomy and subsequent risk of IBD. As always, there are a fantastic range of articles published in BMJOG within the last month and these can all be accessed free-of-charge on the website.

In their excellent paper, Garcia-Argibay and colleagues performed a comparison of incidence of UC and acute appendicitis in a Swedish national cohort of over 3 million people. Using survival analyses and adjusting for a number of confounders the team stratified patients by incidence of appendicitis by the age of 20, and further stratified by siblings to adjust for unmeasured familial and environmental influences. There were nearly 60 million person-years of follow-up, and analyses demonstrated a hazard ratio of 0.37 for development of UC, comparing those who had appendicitis by the age of 20 to those who did not. The overall incidence of UC in the appendicitis group was 1.66 (1.28–2.14) per 10000 person-years, compared to 3.63 (3.59–3.68) per 10000 person-years in those who did not have appendicitis.

After performing the sibling matched analysis, the results demonstrated a marginal attenuation in association, HR=0.46 (95% CI 0.32 to 0.66). Overall, individuals who were diagnosed with appendicitis by the age of 20 showed a reduced risk for developing UC compared with those who had not had appendicitis. As the sibling matched analysis did not demonstrate a significant change in HR, the authors conclude that genetics and shared environmental impacts are modest. Appendicitis, or appendicectomy, or the underlying cause of this, appear to be protective of subsequent UC.

There has been great interest in the role of appendicitis, and appendicectomy, in the subsequent risk of developing IBD. Data is robust enough to have spawned an RCT, the ACCURE-trial, to look at treatment of UC with appendicectomy. Our own analysis of HES data in paediatric populations confirms the reduction of subsequent UC after appendicitis. On the other hand, Crohn’s disease incidence appears to be transiently higher after appendicitis, with most studies attributing this to misdiagnosis of TI Crohn’s disease as an acute presentation of appendicitis. The underlying pathogenesis and relationship of the conditions remains murky and further work is needed. This interesting topic may yet be brought to clinical relevance!

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