Miss rate of colorectal neoplastic polyps and risk factors for missed polyps in consecutive colonoscopies

Background/Aims: Colonoscopic polypectomy is the best diagnostic and therapeutic tool to detect and prevent colorectal neoplasms. However, previous studies have reported that 17% to 28% of colorectal polyps are missed during colonoscopy. We investigated the miss rate of neoplastic polyps and the factors associated with missed polyps from quality-adjusted consecutive colonoscopies. Methods: We reviewed the medical records of patients who were found to have colorectal polyps at a medical examination center of the Kangbuk Samsung Hospital between March 2012 and February 2013. Patients who were referred to a single tertiary academic medical center and underwent colonoscopic polypectomy on the same day were enrolled in our study. The odds ratios (ORs) associated with polyp-related and patient-related factors were evaluated using logistic regression analyses. Results: A total of 463 patients and 1,294 neoplastic polyps were analyzed. The miss rates for adenomas, advanced adenomas, and carcinomas were 24.1% (312/1,294), 1.2% (15/1,294), and 0% (0/1,294), respectively. Flat/sessile-shaped adenomas (adjusted OR, 3.62; 95% confidence interval [CI], 2.40-5.46) and smaller adenomas (adjusted OR, 5.63; 95% CI, 2.84- 11.15 for ≤5 mm; adjusted OR, 3.18; 95% CI, 1.60-6.30 for 6-9 mm, respectively) were more frequently missed than pedunculated/ sub-pedunculated adenomas and larger adenomas. In patients with 2 or more polyps compared with only one detected (adjusted OR, 2.37; 95% CI, 1.55-3.61 for 2-4 polyps; adjusted OR, 11.52; 95% CI, 4.61-28.79 for ≥5 polyps, respectively) during the first endoscopy, the risk of missing an additional polyp was significantly higher. Conclusions: One-quarter of neoplastic polyps was missed during colonoscopy. We encourage endoscopists to detect smaller and flat or sessile polyps by using the optimal withdrawal technique.