Cholecystectomy and the risk of colorectal cancer

OBJECTIVES: Cholecystectomy has been implicated as a possible risk factor for colorectal cancer. However, the clinical evidence and the underlying mechanism for this association are still inconclusive. We conducted a population-based study to further clarify this association. METHODS: We conducted a retrospective cohort study among all patients aged 40 yr or older in the General Practice Research Database from the United Kingdom. We excluded patients with < 1 yr of colorectal cancer-free database follow-up as well as those patients who developed colorectal cancer within 1 yr after their cholecystectomies. Crude and adjusted incidence rate ratios (IRRs) were determined using Poisson regression. RESULTS: The incidence rate of colorectal cancer among cholecystectomy patients (n = 55,960) was 119 (95% CI: 106-133) per 100,000 person-years, compared to 86 (95% CI: 83-90) per 100,000 person-years among patients without a cholecystectomy (n = 574,668). Among the covariates examined, only sex and age were significant confounders and were included in the adjusted analyses. The adjusted IRR of colorectal cancer associated with cholecystectomy was 1.32 (95% CI: 1.16-1.48, p < 0.001). The positive association was present for colon cancer (adjusted IRR 1.51, 95% CI: 1.30-1.74, p < 0.001), but not for rectal cancer (adjusted IRR 1.00, 95% CI: 0.85-1.17, p= 0.99). The pattern of association was similar in men versus women. A similar association with colon cancer was observed for cholelithiasis. CONCLUSIONS: Cholecystectomy is associated with a modestly increased risk of colon cancer but not for rectal cancer. Lithogenic bile could be the underlying mechanism.