Childhood appendectomy is linked with higher digestive, respiratory, and genitourinary disease risk but lower inflammatory bowel disease risk.

Background and objectives: Appendectomy is a common pediatric procedure generally considered safe beyond perioperative risks. However, the appendix may support gut biofilm maintenance and immune function, raising questions about potential long-term health consequences of its removal during childhood. Methodology: We examined associations between appendectomy before age 12 and subsequent risk of 25 disease outcomes between ages 12 and 30, using a population-based cohort of up to 1 071 086 children born in Denmark between 1979 and 1999 and followed through linked national registers until 2009. Stratified Cox regression models compared surgically treated individuals with matched controls without significant pre-surgical health differences. Analyses adjusted for pregnancy complications, parental disease history, birth weight, Apgar score, sex, and socioeconomic factors. Results: Childhood appendectomy was associated with increased risk of several disease categories, particularly digestive [relative risk (RR) 1.45-1.64], respiratory (RR 1.20-1.73), and genitourinary disorders (RR 1.30-1.72). In contrast, inflammatory bowel disease (IBD) risk was reduced (RR 0.58). Absolute risk increases were most notable for digestive (up to 2.81%) and respiratory diseases (up to 4.89%), suggesting measurable population-level associations. Conclusions and implications: Childhood appendectomy is associated with altered long-term disease risk. These findings support evidence that the appendix contributes to digestive and immune function. Although the reduced risk of IBD may represent a beneficial association, our results suggest that the appendix is not functionally redundant, particularly during immune development in childhood.