Unaltered risk of colorectal cancer within 14-17 years of cholecystectomy: updating of a population-based cohort study.

The incidence of colorectal cancer after cholecystectomy was analysed in a historical population-based cohort study comprising 16,439 patients who were completely followed up for 14-17 years after operation. The observed number of colorectal cancers (150) was lower than the expected number of 166.3 (relative risk (RR) = 0.90:95 per cent confidence limits 0.77-1.05) and the overall risk for colon cancer (RR = 0.95) did not differ significantly from that of rectal cancer (RR = 0.82). Separate analyses by sex, age at operation and duration of follow-up revealed relative risks close to or lower than unity. Some deviations indicating a substantially reduced risk might have been due to the play of chance alone. Our results contradict the idea both of a causal and of a non-causal association-through common aetiological factors-between surgically confirmed gallbladder disease and colorectal cancer.