Underwater endoscopic mucosal resection for colorectal lesions: a meta-analysis.

BACKGROUND Underwater endoscopic mucosal resection (UEMR) of colorectal lesions is emerging as an alternative method to conventional endoscopic mucosal resection (CEMR). This study aimed to evaluate the feasibility and safety of UEMR for colorectal lesions. METHODS The PubMed, Embase, Cochrane and Web of Science databases were searched before May 10, 2020. The primary outcomes were en bloc resection rate (feasibility) and adverse event rate (safety). The secondary outcome was recurrence and residual adenoma rate. If there was a comparison between UEMR and CEMR, data about en bloc resection, delayed bleeding, and recurrence and residual adenoma were extracted and compared. The pooling of the effect size was conducted using random-effects models, and the Q-statistic, τ2, and I2 were used to evaluate heterogeneity. RESULTS Seventeen studies (759 patients, 893 lesions) were included. The pooled estimate for the en bloc resection rate was 59% (95% CI 43-75%) with significant heterogeneity (I2 = 97%). Due to the heterogeneity, it is not suitable to conduct pooled estimates analysis, so the en bloc resection rate was from 10 to 89%. The pooled estimate for delayed bleeding was 2% (95% CI, 1%-3%) and only two cases had perforation. The pooled rate of recurrence and residual adenoma was 5% (95% CI 2%-8%). Compared with CEMR, UEMR could achieve a higher en bloc resection rate (OR 1.61; 95% CI 1.02-2.53; p = 0.04) with a lower rate of recurrence and residual adenoma (OR 0.18; 95% CI 0.07-0.46; p < 0.01). CONCLUSIONS UEMR for colorectal lesions was capable of a high en bloc resection rate, low adverse event rate and low recurrence. UEMR may be considered an effective and safe alternative for treating colorectal lesions.