Colonoscopy and colorectal cancer incidence and mortality.

There is substantial indirect evidence for the effectiveness of colonoscopy in reducing colorectal cancer incidence and mortality. However, several recent studies have raised questions on the magnitude of effect for right-sided colorectal cancers. Well-documented variation in outcomes when colonoscopy is performed by different groups of endoscopists suggests that the recent emphasis on the quality of the procedures should lead to improved outcomes after colonoscopy including reduction in incidence and mortality due to right-sided colorectal cancers.