Colon Polyps and Colorectal Cancer Screening

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GI NOTES

Colon Polyps and Colorectal Cancer Screening

Key points

Average-risk screening starts at age 45 and continues to 75; from 76 to 85 decide individually.
The best test is the one that gets done: colonoscopy every 10 years, or yearly FIT, or stool DNA-FIT every 1 to 3 years, or CT colonography every 5 years.
Any positive non-colonoscopy test needs a follow-up colonoscopy, ideally within a few months; the screening is not complete until it is done.
Adenoma detection rate is the key colonoscopy quality measure.
Surveillance intervals depend on the number, size and histology of polyps (USMSTF 2020).

1. Who to screen and when

Risk group	Start	Test and interval
Average risk	Age 45	Any recommended test (see below) until 75
One first-degree relative with CRC or advanced adenoma diagnosed under 60, or two first-degree relatives at any age	Age 40, or 10 years before the youngest relative’s diagnosis	Colonoscopy every 5 years
One first-degree relative diagnosed at 60 or older	Age 40	Average-risk options and intervals
Lynch syndrome	Age 20 to 25 (gene-dependent)	Colonoscopy every 1 to 2 years
IBD colitis	About 8 years after diagnosis (PSC: at diagnosis)	Surveillance colonoscopy every 1 to 3 years

2. Screening tests

Test	Interval	Notes
Colonoscopy	Every 10 years	Diagnostic and therapeutic; needs bowel prep and sedation
Fecal immunochemical test (FIT)	Every year	Cheap, no prep; must be repeated yearly
Multitarget stool DNA-FIT	Every 1 to 3 years	Higher sensitivity than FIT but more false positives
CT colonography	Every 5 years	Needs prep; polyps 6 mm or larger need colonoscopy
Flexible sigmoidoscopy	Every 5 to 10 years	Examines only the distal colon
Blood-based tests	Not a first-line option	Lower sensitivity for advanced adenomas; for people who decline all other tests

3. Colonoscopy quality and polypectomy

Quality measures: adenoma detection rate (current ACG/ASGE target 35% or more for screening exams in people 45 and older), cecal intubation in 95% or more of screening exams, adequate bowel prep in 90% or more, and an average withdrawal time of at least 8 minutes.
Bowel prep: split-dose regimens give the best cleansing. If prep is inadequate, repeat within 1 year.
Polypectomy: cold snare for polyps under 10 mm (cold forceps only for 1 to 2 mm). Endoscopic mucosal resection for large non-pedunculated lesions; refer complex lesions to an expert rather than to surgery.
Clip closure after resection of non-pedunculated lesions 20 mm or larger in the right colon reduces delayed bleeding.

4. Surveillance after polypectomy

FIGURE: NEXT COLONOSCOPY AT A GLANCE (HIGH-QUALITY EXAM, COMPLETE RESECTION)

What was found?

Normal, or small rectosigmoid hyperplastic polyps: 10 years

1 to 2 tubular adenomas under 10 mm: 7 to 10 years

3 to 4 adenomas under 10 mm: 3 to 5 years

Advanced adenoma (10 mm or more, villous, high-grade dysplasia) or 5 to 10 adenomas: 3 years

Original diagram based on the 2020 US Multi-Society Task Force recommendations.

Finding	Next colonoscopy
1 to 2 tubular adenomas under 10 mm	7 to 10 years
3 to 4 tubular adenomas under 10 mm	3 to 5 years
5 to 10 tubular adenomas under 10 mm	3 years
Adenoma 10 mm or larger, tubulovillous or villous, or high-grade dysplasia	3 years
More than 10 adenomas	1 year; consider genetic testing
Piecemeal resection of a lesion 20 mm or larger	6 months
Hyperplastic polyp 10 mm or larger	3 to 5 years
1 to 2 sessile serrated lesions under 10 mm	5 to 10 years
Sessile serrated lesion 10 mm or larger, with dysplasia, or traditional serrated adenoma	3 years

5. High-yield pearls

Iron deficiency anemia or rectal bleeding in any adult is a diagnostic, not a screening, colonoscopy.
Sessile serrated lesions are flat, right-sided and easy to miss; they drive many interval cancers.
A FIT-positive result followed by a long delay to colonoscopy increases cancer risk; aim to scope promptly.
Early-onset colorectal cancer is rising: take red-flag symptoms seriously in people under 45.

Self-check questions

When should a person whose father had colon cancer at 52 start screening, and how?
Two 5 mm tubular adenomas were removed. Next colonoscopy?
A 25 mm flat lesion was removed piecemeal. Next colonoscopy?
A FIT is positive. What next?

Answers: (1) At age 40 (10 years before 52 would be 42, so the earlier of the two, 40), with colonoscopy every 5 years. (2) 7 to 10 years. (3) 6 months. (4) Colonoscopy, ideally within a few months.

References

US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(19):1965-1977.
Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK. ACG Clinical Guidelines: Colorectal Cancer Screening 2021. Am J Gastroenterol. 2021;116(3):458-479.
Gupta S, Lieberman D, Anderson JC, et al. Recommendations for Follow-Up After Colonoscopy and Polypectomy: A Consensus Update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology. 2020;158(4):1131-1153.
Rex DK, Anderson JC, Butterly LF, et al. Quality indicators for colonoscopy. Am J Gastroenterol. 2024;119(9):1754-1780.

For educational purposes only. This note does not replace clinical judgment or local protocols. Check doses against current labeling and institutional guidance.