Background: Although current quality indicators of colonoscopy recommend 6 minutes as the minimum standard for withdrawal time (WT), long-term implementation of the 6-minute WT results in low colonoscopy turnaround efficiency and it don't take into account the effects of endoscopists experience and the quality of bowel preparation of colonoscopy .Whether it is still necessary to adhere to the 6-minute WT standard under the condition of experienced endoscopists and excellent bowel preparation quality is worthy of further discussion. Therefore, this study based experienced endoscopists and excellent bowel preparation (Boston Bowel Preparation Scale score, BBPS≥8) is aimed to compare the effects of 5-minute WT versus 6-minute WT on adenoma detection rate (ADR) and adenoma miss rate (AMR).

Methods: This multicenter, randomized controlled trial involving 423 patients was conducted from June 2023 to March 2025 in 5 centers, including Wuxi People's Hospital, Jiangsu Province People's hospital, Xuzhou First People's Hospital, The Second Affiliated Hospital of Soochow University, Taizhou People's Hospital. Colonoscope was inserted and withdrew twice on each patient and all procedures for the same patient were done by the same endoscopist. Participants were randomly divided into the 5-minute WT group (the first WT-5-minute and the second WT-6-minute, n =214) and the 6-minute WT group (the first WT-6-minute and the second WT-6-minute, n=209), and a timer was used to adjust the withdrawal speed. The primary outcome was ADR and AMR. 

Results: The baseline characteristics of the two groups were similar (Table 1) and colonoscopy characteristics of the patients in the two groups regarding quality of bowel preparation, cecal intubation rate, cecal intubation time, cecal intubation distance, number of abdominal compression, number of position change were comparable (Table 2). Overall ADR(39.7% vs 43.5%，P = 0.425), ADR in the first (36.0% vs 36.4%，P = 0.935) and second withdrawal (10.7% vs 13.9%，P = 0.327) were not significantly increased in the 6-minute WT group compared with the 5-minute WT group. Likewise, the overall advanced adenoma detection (AADR) (4.7% vs 5.3%，P = 0.780), AADR in the first (4.7% vs 5.3%，P = 0.780) and second withdrawal (0.5% vs 0.5%，P = 0.745) did not differ statistically. Further analysis showed that AMR (10.7% vs 13.9%，P = 0.372) was lower in the 5-minute WT group than in the 6-minute WT group, less adenomas were missed in the 5-minute WT group, although not statistically significant (Table 3).

Conclusion: Shortening WT from 6 to 5 minutes didn't reduce ADR based experienced endoscopists and excellent BBPS, a 5-minute WT benchmark was acceptable with experienced endoscopists and excellent bowel preparation quality of colonoscopy.