Rate and risk factors of missed diagnosis of colorectal adenoma with colonoscopy

Objective To investigate the miss rate of adenoma with colonoscopy and assess the features and risk factors for missed diagnosis.Methods Patients with colorectal adenoma received a second colonoscopy within 120 days after adenoma was detected and removed on the initial colonoscopy.The findings of two colonoscopies were reviewed and analyzed.The features of adenoma （including size, location, shape, number and pathology） , clinical characteristics of patients （including age, sex, reasons of colonoscopy, history of diverticular disease, history of abdominal or pelvic surgery and colonoscopy with sedation） and endoscopists were recorded.Miss rate and features of different types of missed adenoma were analyzed.We also assessed the effects of adenoma features, patients＇ characteristics and endoscopists on missed diagnosis of adenoma.Results Adenoma missed diagnosis was found in 271 patients out of 809 recruited subjects （33% ）.A total of 425 adenomas were missed out of 2134 （20% ） adenomas detected by repeated colonoscopy.A large diameter was associated with a decrease in the miss rate for adenoma （P 〈 0.01）.Conversely , sessile or flat shape （P 〈 0.01） , locations at sigmoid, hepatic flexure, cecum and ascending colonic （ P 〈 0.05） were significantly associated with a higher miss rate of adenoma, as was the number of adenomas （P 〈0.01）.A higher adenoma missed diagnosis rate was observed in beginner colonoscopists, as compared with experienced ones （P 〈 0.01）.Conclusion A marked miss rate of adenoma exists on colonoscopy, which is significantly associated with the size, shape, location and number of adenomas and endoscopists. Key words: Colonoscopy;  Adenomatous polyposis coli;  Miss rate