Realistic Expectations After Negative Colonoscopy

Gastroenterologists and the public have embraced the idea that colonoscopy can prevent most colorectal cancers. The idea was first proposed after the recognition that the majority of colorectal cancer began with benign adenomas—the so-called adenoma carcinoma sequence.¹ Removing adenomas could interrupt the sequence and potentially prevent cancer. Indeed, publication of results from the National Polyp Study offered evidence that colonoscopic polypectomy could reduce the incidence of colorectal cancer.² However, there remain unanswered questions. How long are patients protected after a negative colonoscopy? Is the protection comparable for the right and left colon? How much is the risk reduced?