More than 60 epidemiologic studies have investigated a possible relation between cholecystectomy and colon cancer risk. However, the strength of any association remains uncertain because of the small size and retrospective design with a failure to control for potential confounders of most analyses. A meta-analysis of studies conducted through 1993 (Giovannucci et al, 1993) observed a modest increase in the risk of colorectal cancer following cholecystectomy, although the effect was restricted primarily to the proximal colon. Two subsequent meta-analyses (Bollschweiler et al, 1993; Reid et al, 1996) and three large prospective cohort studies (Ekbom et al, 1993; Goldbohm et al, 1993; Lagergren et al, 2001) also observed an increased risk of proximal cancers, particularly among women.

Most studies that examined the relation between gallstones or cholecystectomy and colorectal cancer did not adjust for other risk factors for colorectal cancer, including diet. Therefore, among those studies demonstrating a positive association, one cannot exclude potential confounding by dietary or other lifestyle factors that are jointly associated with gallstones and colorectal cancer.

For the relation between cholecystectomy and colorectal cancer to be adequately characterised, large cohort studies with a long duration of follow-up and adequate assessment of potential confounding factors are necessary. We therefore utilised data from a prospective cohort study among women to illuminate further the influence of gallstones and cholecystectomy on the risk for colorectal cancer and distal colorectal adenoma.