Detection of colonic polyps according to insertion/withdrawal phases of colonoscopy

Issues on colonoscopy quality are crucial to reduce the advanced neoplasia miss rate of colonoscopy. Recently, a > 6-min withdrawal time has been recommended. However, the relative prevalence of polyp detected during insertion and withdrawal phases of colonoscopy is unknown. Therefore, we designed this prospective, endoscopic study. Three hundred and sixty-eight patients with 396 adenomas were selected from a consecutive colonoscopic series of 1,205 cases. Detection rates of adenomas, advanced adenomas, and cancer according to withdrawal and insertion phases of colonoscopy, also subgrouping polyps for size and location, were compared. Thirty-two (74%) advanced adenomas and 21 (95%) cancers were detected during the insertion, being only 11 (26%) and one (5%) identified during withdrawal, respectively. This was mainly due to a higher detection of > 10 mm polyps during insertion than during withdrawal (75% versus 25%). Most advanced neoplasia are detected during the insertion. Although withdrawal time has been shown to be important, the scope insertion phase related to polyp detection should be specifically addressed.