Most large colorectal polyps missed by gastroenterology fellows at colonoscopy are sessile serrated lesions

Background and study aims: Data on adenoma and sessile serrated lesion (SSL) miss rates for gastroenterology fellows during colonoscopy are limited. We aimed to describe the miss rate of fellows based on a second examination by a colonoscopist with a high rate of detection. Patients and methods: Second- and third-year gastroenterology fellows at a single, tertiary center performed initial examinations. A single experienced attending doctor then performed a complete examination of the colon. We recorded the size and pathology of all lesions found at both examinations and calculated the adenoma and SSL miss rates for fellows. Results: Ten trainees performed 100 examinations. Miss rates for conventional adenomas and SSLs were 30.5 % and 85.7 %, respectively. Among pre-cancerous polyps ≥ 10 mm, 10 of 14 lesions missed were SSLs. Conclusions: While conventional adenoma detection skills of gastroenterology fellows are acceptable, SSL detection is poor.