Appendectomy, acute appendicitis, and gastrointestinal diseases: A Mendelian randomization study

Background: Appendectomy is the standard treatment for acute appendicitis. However, the effects of appendectomy and acute appendicitis on gastrointestinal diseases are not fully understood. Methods: Genetic variants associated with appendectomy and acute appendicitis at a genome-wide significance level (P < 5.0E-08) were selected as instrumental variables. Two-sample univariate and multivariate Mendelian randomization (MR) analyses were performed to examine the independent effects of appendectomy and acute appendicitis on related gastrointestinal diseases. Results: Appendectomy was linked to an increased risk of colon cancer (odds ratio [OR], 1.54; 95 % confidence interval [CI], 1.15-2.07; P = 0.004; FDR-corrected P = 0.016) and a decreased risk of primary sclerosing cholangitis (OR, 0.57; 95 % CI, 0.38-0.84; P = 0.004; FDR-corrected P = 0.016). Acute appendicitis was associated with a higher risk of cholelithiasis (OR, 1.16; 95 % CI, 1.06-1.27; P = 0.002; FDR-corrected P = 0.016). Conclusion: This study suggested that appendectomy and acute appendicitis might affect the risk of several gastrointestinal diseases in European populations.