Abstract :
Background: High definition (HD) colonoscopy may better detect colorectal polyps. However, polyps
can be easily missed, and this may account for an interval cancer. There are other reasons also for missed polyps,
including endoscopist’s factors, technical factors, and polyps characters, etc.
Objective: To evaluate colorectal polyp miss rates by using HD colonoscope (Olympus CF-HQ190) for
same-day back-to-back colonoscopies and to identify other independent factors for missed polyps.
Method: Between January 2014 and November 2014, back-to-back colonoscopies in asymptomatic
subjects aged 50-75 years were performed in a randomized order by four different experienced endoscopists with
more than 1,000 colonoscopies and with previous record of adenoma detection rate (ADR)>25%. During each
round of colonoscopy, detected polyps were removed either by means of a biopsy forceps or a snare. The results of
the first-round colonoscopy were blinded to the following endoscopists. All polyps detected and removed by the
first or the second endoscopists were recorded. The quality of bowel preparation, withdrawal time, location, size
and histology of polyps were recorded. Advanced adenoma (AA) was defined as an adenoma with size ≥10 mm or
an adenoma with high-grade dysplasia or villous histology. The polyp miss rate was calculated as the total number
of polyps missed from the first colonoscopy/the total number of polyps detected by both the first and the second
colonoscopists.
Results: One-hundred-and-nine subjects were enrolled, and 218 complete colonoscopies were performed.
One-hundred-and-six (97%) of subjects had good to excellent bowel preparation. The mean withdrawal times of
the first and the second colonoscopies were 12.5 ± 10 and 9.1±2.9 min, respectively. The overall detection rate of
adenoma, advanced adenoma and cancer were 48%, 13% and 1%, respectively. Of all 109 subjects, 306 polyps
were found in 84 subjects. Among 306 polyps, there were 140 (45.8%) non-adenoma, 166 (54.2%) adenoma. There
were 32 (10.4%) AA and 1 (0.3%) cancer. The miss rates for non-adenoma, adenoma and AA were 26.8%, 28.3%
and 21.9%, respectively. No carcinoma was missed. In the univariate analysis, non-pedunculated lesion and the
withdrawal time < 9 min were the significant factors for polyps miss rate. There was a trend of higher miss rate for
proximal polyp location and for polyp size ≤5 mm, but not statistically significant. In the multivariate analysis, the
independent significant associated factors for polyps miss rate were non-pedunculated lesion [Odd ratio 11.49
(95% CI: 1.44-91.59); p= 0.02] and duration of withdrawal time less than 9 min. [Odd ratio 3.02 (95% CI: 1.67-
5.45); p<0.001].
Conclusion: Under HD colonoscopy, polyp miss rate still occurs. Non-pedunculated lesions and the
withdrawal time less than 9 minutes were the significant factors for this phenomenon.
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file/Thai-Journal-of-gastroenterology-vol-16-no-2-2058394.pdf