Associations of cholecystectomy with the risk of colorectal cancer: a Mendelian randomization study

BACKGROUND: Cholecystectomy is a standard surgery for patients suffering from gallbladder diseases, while the causal effects of cholecystectomy on colorectal cancer (CRC) and other complications are still unknown. METHODS: We obtained genetic variants associated with cholecystectomy at a genome-wide significant level (P value <5 × 10(−8)) as instrumental variables (IVs) and performed Mendelian randomization (MR) to identify the complications of cholecystectomy. Furthermore, the cholelithiasis was also treated as the exposure to compare its causal effects to those of cholecystectomy, and multivariable MR analysis was carried out to judge whether the effect of cholecystectomy was independent of cholelithiasis. The study was reported based on Strengthening the Reporting of Observational Studies in Epidemiology Using Mendelian Randomization guidelines. RESULTS: The selected IVs explained 1.76% variance of cholecystectomy. Our MR analysis suggested that cholecystectomy cannot elevate the risk of CRC (odds ratio [OR] =1.543, 95% confidence interval [CI]: 0.607–3.924). Also, it was not significant in either colon or rectum cancer. Intriguingly, cholecystectomy might decrease the risk of Crohn's disease (OR = 0.078, 95% CI: 0.016–0.368) and coronary heart disease (OR = 0.352, 95% CI: 0.164–0.756). However, it might increase the risk of irritable bowel syndrome (IBS) (OR = 7.573, 95% CI: 1.096–52.318). Cholelithiasis could increase the risk of CRC in the largest population (OR = 1.041, 95% CI: 1.010–1.073). The multivariable MR analysis suggested that genetic liability to cholelithiasis could increase the risk of CRC in the largest population (OR = 1.061, 95% CI: 1.002–1.125) after adjustment of cholecystectomy. CONCLUSIONS: The study indicated that cholecystectomy might not increase the risk of CRC, but such a conclusion needs further proving by clinical equivalence. Additionally, it might increase the risk of IBS, which should be paid attention to in clinical practice.