Underwater Versus Conventional Endoscopic Mucosal Resection for ≥10 Mm Sessile or Flat Colorectal Polyps: A Systematic Review and Meta-Analysis

Background and aimUnderwater 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.MethodsPubMed, 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.ResultsNine 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.ConclusionUEMR 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.