9 Minutes for Tandem Colonoscopy Withdrawal

A mean withdrawal time of at least 6 minutes has been considered to be one of the critical quality criterions of colonoscopy. Recently, our group completed a multicenter randomized controlled trial, which proved that prolonging the withdrawal time to 9 minutes could significantly improve the adenoma detection rate of colonoscopists, especially for young colonoscopists and proximal colon. However, it has some limitations in included participates (mixed indications for colonoscopy) and cannot illustrate the impact of withdrawal time on adenoma miss rate in a parallel randomized design. It is necessary to include tandem colonoscopy and adopt strict criteria of the screening population to confirm the effect of the 9-minute withdrawal time on the adenoma miss rate. Therefore, the investigators plan to conduct a multicenter, randomized controlled trial of tandem colonoscopy to compare adenoma miss rate of 6-minute and 9-minute withdrawal in screening population.