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Am Fam Physician. 2021;103(5):314-316

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Key Points for Practice

• Adenomas on initial colonoscopy affect ongoing follow-up screening recommendations.

• A single normal colonoscopy demonstrates a lifetime CRC mortality risk 68% lower than in the general population.

• Finding more than 10 adenomas confers the highest risk, and repeat colonoscopy is recommended in one year.

• Finding polyps larger than 10 mm, between five and 10 sessile serrated polyps or adenomas, polyps with dysplasia, or traditional serrated adenomas confers high risk, and repeat colonoscopy is recommended in three years.

From the AFP Editors

Screening colonoscopy findings define the future risk of colorectal cancer (CRC) and the need for repeat screening. The U.S. Multi-Society Task Force on Colorectal Cancer updated recommended follow-up intervals after screening colonoscopy in average-risk individuals. This guidance does not apply to people with hereditary syndromes that increase CRC risk, inflammatory bowel disease, serrated polyposis syndrome, or personal or family history of CRC. Although tobacco use, rural living, metabolic syndrome, obesity, and aspirin use affect CRC risk, they do not influence recommended screening intervals.

Adequate Study

The task force defines an adequate study as a high-quality colonoscopy, which requires bowel preparation sufficient to visualize all polyps larger than 5 mm, examination to the cecum, and complete excision of all polyps found. Physicians who perform high-quality colonoscopies should detect adenomas in more than 30% of men and 20% of women who are screened.

Colonoscopy Findings Determine Risk

Common findings on colonoscopy reports include adenomas and polyps. Instead of defining high- and low-risk findings, task force recommendations depend on the number and size of findings.

When patients have had more than one colonoscopy, adenomas on initial colonoscopy are the most significant indicator of risk, affecting ongoing follow-up screening recommendations. Recommended intervals for screening based on the current findings may be shortened if a previous colonoscopy showed higher risk. The guideline includes recommendations based on limited evidence for a second follow-up depending on findings of the initial and original follow-up colonoscopies (Table 1).

Initial colonoscopy findingFollow-up interval, yearsFollow-up colonoscopy findingFollow-up interval, years
Normal (no polyps)10
Traditional adenomas
Tubular adenomas < 10 mm
1 to 27 to 10Normal10
Tubular adenomas < 10 mm
1 to 27 to 10
3 to 43 to 5
5 to 103
High-risk adenoma3
3 to 43 to 5Normal10
Tubular adenomas < 10 mm
1 to 27 to 10
3 to 43 to 5
5 to 103
High-risk adenoma3
5 to 103No evidence available
High-risk adenoma ≥ 10 mm or villous or tubulovillous histology, or high-grade dysplasia3Normal5
Tubular adenomas < 10 mm
1 to 25
3 to 43 to 5
5 to 103
High-risk adenoma3
> 101No evidence available
Serrated polyps
Sessile serrated polyps < 10 mm
1 to 25 to 10No evidence available
3 to 43 to 5No evidence available
5 to 103No evidence available
High-risk sessile serrated polyp ≥ 10 mm or dysplasia3No evidence available
Hyperplastic polyps
Up to 20 polyps < 10 mm10No evidence available
Any polyps ≥ 10 mm3 to 5No evidence available
Traditional serrated adenoma3No evidence available

Normal Colonoscopy

A normal colonoscopy report can include hyperplastic polyps less than 10 mm in diameter, but no other findings. A single normal colonoscopy denotes a lifetime CRC mortality risk 68% lower than the general population. Although there is no direct evidence of benefit, the group recommends a 10-year follow-up after a normal study.

Tubular Adenomas

Tubular adenomas include all nonserrated lesions. Adenomas that are at least 10 mm in diameter or that have pathology reported as tubulovillous, villous, or high-grade dysplasia are at high risk of neoplasia at follow-up. For these lesions, repeat colonoscopy is recommended at three years. For large adenomas, repeat colonoscopy leads to lower future CRC risk.

Without high-risk findings, recommendations depend on the number of adenomas. For one to two adenomas, a seven- to 10-year follow-up interval is recommended. Recent studies have shown that these patients have CRC risks similar to patients with normal colonoscopy. For three to four adenomas, a three- to five-year follow-up is recommended because studies suggest risk is only slightly higher than with one or two adenomas. For five to 10 adenomas, a three-year follow-up is recommended because of higher neoplasia risk in this population.

When more than 10 adenomas are found, a hereditary polyposis syndrome is likely, and repeat colonoscopy is recommended in one year. In one study, people with this finding had about a 25% risk of developing advanced neoplasia at four years.

Serrated Lesions

Serrated lesions have a similar histologic appearance and are identified as sessile serrated polyps, traditional serrated adenomas, and hyperplastic polyps on pathology reports. The neoplasia risk after finding serrated lesions is not as well defined as the risk with tubular adenomas.

SESSILE SERRATED POLYPS

The neoplasia risk after finding sessile serrated polyps appears to be less than for tubular adenomas. When sessile serrated polyps are at least 10 mm in diameter or have dysplasia, risk appears to be high and a three-year follow-up is recommended. Without these features, follow-up depends on the number of lesions. For one to two polyps, a five- to 10-year follow-up colonoscopy is recommended. This interval is three to five years with three to four sessile serrated polyps and three years with five to 10 polyps.

TRADITIONAL SERRATED ADENOMAS

Traditional serrated adenomas confer a higher neoplasia risk than tubular adenomas, so a three-year follow-up colonoscopy is recommended when they are found.

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