Colorectal cancer after cholecystectomy: absence of risk increase within 11-14 years.

The importance of cholecystectomy as a risk factor for colorectal cancer was analyzed in an historical cohort study covering 16,773 cases during 11-14 years completed after operation. The observed number of colorectal cancers (130) was lower than the expected 153.5 [relative risk (RR) = 0.85]. For cancer of the colon, the observed number was 87, which was near the 91 expected (RR = 0.95). A significantly increased risk (p less than 0.05; RR = 2.86) was found for cancer of the colon only during the first year after cholecystectomy, and this was judged to be due to cancers present but overlooked at the time of cholecystectomy. The incidence of rectal cancer was significantly decreased (RR = 0.69; p less than 0.05), with 43 observed versus 62.4 expected cases. The distribution of right-sided versus left-sided cancers within the cohort did not differ significantly from that in the general population. Our results do not as yet support previous epidemiologic observations of an increased risk of colorectal cancer after cholecystectomy.