Childhood appendicitis and future risk of inflammatory bowel disease - A nationwide cohort study in Sweden 1973-2017

Aim The aim of this study was to investigate the association between juvenile appendicitis, treated conservatively or with appendectomy, and adult risk of inflammatory bowel disease (IBD), either ulcerative colitis (UC) or Crohn's disease (CD). We used nationwide population data from more than 100,000 individuals followed for over four decades. Method All Swedish patients discharged with a diagnosis of appendicitis before the age of 16 years between 1973 to 1996 were identified. Everyone diagnosed with appendicitis was matched to an individual in the general population without a history of juvenile appendicitis (unexposed) of similar age, sex and region of residence. The study population was retrospectively followed until 2017 for any development of UC or CD. Cox proportional-hazards models compared disease-free survival time between exposed and unexposed individuals, also analysing the impact of treatment (conservative treatment versus appendectomy). Results The final cohort consisted of 52,391 individuals exposed to appendicitis (1,674,629 person years) and 51,415 unexposed individuals (1,638,888 person years). Childhood appendicitis with appendectomy was associated with a significantly lower risk of adult IBD [adjusted hazard ratio (aHR) 0.48 (0.42-0.55)], UC [aHR 0.30 (0.25-0.36)] and CD [aHR 0.82 (0.68-0.97)]. Those treated conservatively had a lower risk of adult UC [aHR 0.29 (0.12-0.69)] but not CD [aHR 1.12 (0.61-2.06)] compared with unexposed individuals. Conclusion Juvenile appendicitis treated with appendectomy was associated with a decreased risk of adult IBD, both UC and CD. Those treated conservatively instead of with surgery had a lower risk of UC only. Our findings warrant more research on the role of the appendix and gut microbiota in the pathogenesis of IBD.