Large Tandem Study Shows 9-Minute Withdrawal Time Better Than 6 Minutes

Large Tandem Study Shows 9-Minute Withdrawal Time Better Than 6 Minutes

Douglas K. Rex, MD, MASGE, reviewing Zhao S, et al. Am J Gastroenterol 2022 Oct 10.

In a randomized tandem study from China, 2 study arms compared the standard colonoscopy withdrawal time of 6 minutes versus 9 minutes. The colon was classified into 3 segments, with a timer sounding 1 minute before the target time. Washing and suctioning were included in the inspection times. 

The 9-minute withdrawal time was associated with a reduction in the adenoma miss rate (AMR) at both the lesion level (14.5% vs 36.6%) and the participant level (10.9% vs 25.9%). There also were reductions in the advanced AMR (5.3% vs 46.9%) and the rate for missing multiple adenomas (20.7% vs 56.5%). There was no clear benefit to prolonging withdrawal time from 6 to 9 minutes for endoscopists with the highest adenoma detection rates. Many other endpoints were examined and essentially all looked like 9 minutes produced better detection.

Douglas K. Rex, MD, FASGE


This study was a massive undertaking and provides clear general support for prolonging the recommended minimum average withdrawal time to 9 minutes.

Note to readers: At the time we reviewed this paper, its publisher noted that it was not in final form and that subsequent changes might be made.


Zhao S, Song Y, Wang S, et al. Reduced adenoma miss rate with 9-minute vs. 6-minute withdrawal times for screening colonoscopy: a multicenter randomized tandem trial: nine-minute WT reduces the AMR of screening colonoscopy. Am J Gastroenterol 2022 Oct 10. (Epub ahead of print) (

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