Skip to Main Content


The US Multi-Society Task Force Guideline provide the following recommendations for repeat colonoscopy that depend on the findings at baseline colonoscopy:

  • 10 years: normal colonoscopy or fewer than 20 hyperplastic polyps < 10 mm in the distal colon or rectum

  • 7-10 years: 1–2 adenomas < 10 mm

  • 5-10 years: 1–2 sessile serrated polyps < 10 mm

  • 3-5 years: 3–4 adenomas or sessile serrated polyps < 10 mm

  • 3 years: 5–10 adenomas or sessile serrated polyps < 10 mm; or 1 or more adenomas or sessile serrated polyp ≥ 10 mm or an adenoma containing villous features or high-grade dysplasia or a sessile serrated polyp with dysplasia.

Adenomas and serrated polyps may be non-polypoid (flat, slightly elevated, or depressed), sessile, or pedunculated (containing a stalk). Their significance is that over 95% of cases of adenocarcinoma of the colon are believed to arise from these lesions. Early detection and removal of these precancerous lesions through screening programs has resulted in a 34% reduction in deaths from colorectal cancer since 2000. It is proposed that there is a polyp → carcinoma sequence whereby nonfamilial colorectal cancer develops through a continuous process from normal mucosa to adenomatous or serrated polyp and later to carcinoma. An estimated 75% of cancers arise in adenomas after inactivation of the APC gene leads to chromosomal instability and inactivation or loss of other tumor suppressor genes. The remaining 25% of cancers arise through the serrated pathway in which hyperplastic polyps develop Kras mutations (forming traditional serrated adenomas) or BRAF oncogene activation (forming sessile serrated lesions) with widespread methylation of CpG-rich promoter regions that leads to inactivation of tumor suppressor genes or mismatch repair genes (MLH1) with microsatellite instability.

A. Adenomas

Adenomas (eFigures 15–32 and 15–33) are present in more than 30% of men and 20% of women over the age of 50. Most adenomas are smaller than 5 mm and have a low risk of becoming malignant. Adenomas are classified as “advanced” if they are 1 cm or larger or contain villous features or high-grade dysplasia. In the general population, the prevalence of advanced adenomas is 6%. Advanced lesions are believed to have a higher risk of harboring or progressing to malignancy. It has been estimated from longitudinal studies that it takes an average of 5 years for a medium-sized polyp to develop from normal-appearing mucosa and 10 years for a gross cancer to arise.

eFigure 15–32.

Diminutive sessile colonic adenoma characterized by a variegated mucosal surface. (Used, with permission, from Y. Chen.)

eFigure 15–33.

Diminutive sessile colonic adenoma visualized under blue light imaging to characterize a prominent mottled vascular pattern. (Used, with permission, from Y. Chen.)

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.