Study details and characteristics.

Background and aim
Underwater endoscopic mucosal resection (UEMR) has been an emerging substitute for conventional EMR (CEMR). This systematic review and meta-analysis aimed at comparing the efficiency and safety of the two techniques for removing ≥10 mm sessile or flat colorectal polyps.
Methods
PubMed, Cochrane Library and Embase databases were searched up to February 2023 to identify eligible studies that compared the outcomes of UEMR and CEMR. This meta-analysis was conducted on the en bloc resection rate, R0 resection rate, complete resection rate, procedure time, adverse events rate and recurrence rate.
Results
Nine studies involving 1,727 colorectal polyps were included: 881 were removed by UEMR, and 846 were removed by CEMR. UEMR was associated with a significant increase in en bloc resection rate [Odds ratio(OR) 1.69, 95% confidence interval(CI) 1.36–2.10, p<0.00001, I2 = 33%], R0 resection rate(OR 1.52, 95%CI 1.14–2.03, p = 0.004, I2 = 31%) and complete resection rate(OR 1.67, 95%CI 1.06–2.62, p = 0.03, I2 = 0%) as well as a significant reduction in procedure time(MD ‒4.27, 95%CI ‒7.41 to ‒1.13, p = 0.008, I2 = 90%) and recurrence rate(OR 0.52, 95%CI 0.33–0.83, p = 0.006, I2 = 6%). Both techniques were comparable in adverse events rate.
Conclusion
UEMR can be a safe and efficient substitute for CEMR in removing ≥10 mm sessile or flat colorectal polyps. More studies verifying the advantages of UEMR over CEMR are needed to promote its application.