Abstract:
Background: The high definition (HD) colonoscope may better detect colorectal polyp. However, the missing polyp could happen and this may result to an interval cancer. There are other reasons for the missing including endoscopists factors, technical factors, and polyps characters, etc. Objective: To evaluate the miss rate of colorectal polyp by using the HD colonoscope (Olympus CF-HQ190) during the same-day back-to-back colonoscopies and to identify the independent factors for the missed polyps. Methods: Between January 2014 to November 2014, back-to-back colonoscopies in asymptomatic subjects aged 50-75 years were performed in a randomized order by four different experienced endoscopists who had performed more than 1,000 colonoscopies with the previous record of ADR > 25%. During each round all detected polyps were removed either by biopsy forceps or snare. The results of the first-round colonoscopy were blinded to the following endoscopists. All polyps detected and removed by the first or second endoscopist were recorded. A quality of bowel preparation, withdrawal time, location, size and histology of polyps were recorded. Advanced adenoma (AA) was defined as an adenoma with size ≥10mm 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 colonoscopies. Results: 109 subjects were enrolled, and 218 complete colonoscopies were performed. 106 (97%) of subjects had good to excellent bowel preparation. The mean withdrawal times of the first and the second colonoscopies were 12.5 + 10 min and 9.1+ 2.9min, respectively. The overall detection rate of adenoma, advanced adenoma and cancer were48 %, 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 polyp, 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 of miss rate for polyp. There were trends of higher miss rate in the proximal polyp and the polyp size ≤5mm but there were not statistically significant. In the multivariate analysis, the independent significant associated factors for miss rate of polyp 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]. Conclusions: Under the HD colonoscope, the miss rate of polyps still occurs. Non-pedunculated lesion and the withdrawal time less than 9 minutes were the significant factors for this phenomenon.