Underwater versus conventional polypectomy for colorectal polyps 10 mm or smaller: a systematic review and meta-analysis of randomized controlled trials.

Underwater polypectomy has emerged as an alternative to conventional polypectomy for the removal of colorectal polyps. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the comparative efficacy and safety of underwater polypectomy and conventional polypectomy. We systematically searched PubMed, Embase, Cochrane Library, and Web of Science for RCTs comparing underwater polypectomy and conventional polypectomy for colorectal polyps. We restricted the analysis to polyps 10 mm or smaller. The primary outcome was en bloc resection rate. Secondary outcomes included incomplete resection, piecemeal resection, R0 resection, intraprocedural bleeding, and resection time. Risk ratios with 95% confidence intervals (CI) were calculated for binary outcomes, and standardized mean differences for continuous outcomes using random-effects models. Four RCTs contributed 1166 polyps 10 mm or smaller (598 underwater polypectomy, 568 conventional polypectomy). Underwater polypectomy and conventional polypectomy showed comparable en-bloc resection rates (risk ratio: 1.01, 95% CI: 0.97-1.05; I2 = 68.9%). Underwater polypectomy was associated with significantly lower incomplete resection rates (risk ratio: 0.38, 95% CI: 0.25-0.56; I2 = 0%). R0 resection favored underwater polypectomy (risk ratio: 1.16, 95% CI: 1.00-1.34; I2 = 85.8), although substantial heterogeneity limits interpretation. Intraprocedural bleeding and resection time did not differ between techniques. Underwater polypectomy demonstrates a significant advantage over conventional polypectomy in reducing incomplete resection rates while maintaining comparable en bloc resection rates and safety profiles. These findings support underwater polypectomy as a reasonable and, in specific settings, preferable alternative to conventional cold snare polypectomy.