Colonoscopy Surveillance After Single 1.2 cm Tubular Adenoma
The appropriate surveillance interval is 3 years (Answer C). This patient has a single tubular adenoma ≥10 mm (1.2 cm), which classifies them as having a high-risk adenoma requiring more intensive surveillance.
Risk Stratification
The size of the adenoma is the critical determining factor here:
- Any adenoma ≥10 mm automatically qualifies as an advanced/high-risk adenoma, regardless of histology or dysplasia grade 1, 2
- This patient's 1.2 cm tubular adenoma places them in the high-risk category, triggering a 3-year surveillance interval 1, 2
- The 2014 Multi-Society Task Force guidelines explicitly state that tubular adenomas ≥10 mm require repeat colonoscopy in 3 years 1
Why Not Other Intervals?
Not 5-10 years: The longer intervals (5-10 years) are reserved only for low-risk adenomas, defined as 1-2 small tubular adenomas <10 mm 1, 2. This patient's polyp exceeds this size threshold.
Not 6 months: Short intervals (2-6 months) are indicated only when piecemeal resection was performed to verify complete removal 1, 3. The question does not indicate piecemeal removal.
Not 10 years: This interval is for patients with no adenomas or only hyperplastic polyps in the rectum/sigmoid 1.
Critical Quality Assumptions
This 3-year recommendation assumes 1, 2:
- Complete examination to cecum with adequate bowel preparation
- Complete polyp removal with high confidence
- Minimum 6-minute withdrawal time
If piecemeal resection occurred (not stated in this case), a 2-6 month follow-up would first be needed to verify complete removal before establishing the 3-year surveillance schedule 1, 3.
Subsequent Surveillance Strategy
- If the 3-year follow-up colonoscopy shows normal findings or only 1-2 small (<10 mm) tubular adenomas with low-grade dysplasia, the next interval can be extended to 5 years 1, 2
- If high-risk features recur, another 3-year interval is indicated 2, 4
Common Pitfall
Do not confuse size thresholds: The distinction between <10 mm and ≥10 mm is absolute. A 1.2 cm (12 mm) adenoma cannot be managed with the 5-10 year interval used for smaller polyps, even though it has favorable tubular histology 1, 2. Size ≥10 mm alone defines high-risk status and mandates 3-year surveillance.