Efficacy and histologic accuracy of underwater versus conventional endoscopic mucosal resection for large (>20 mm) colorectal polyps: a comparative review and meta-analysis

Major limitations with conventional EMR (C-EMR) include high rates of polyp recurrence and low en-bloc resection rates, especially for lesions >20 mm in size. Underwater EMR (U-EMR) has emerged as an alternate technique for en-bloc resection of larger lesions. We conducted a systematic review and meta-analysis comparing the efficacy and safety of the 2 techniques.Multiple databases were searched through June 2020 for studies that compared outcomes of U-EMR and C-EMR for colorectal lesions. Meta-analysis was performed to determine pooled odds ratios (ORs) of successful R0, en-bloc, and piecemeal resection of colorectal lesions. We compared the rates of polyp recurrence at follow-up, diagnostic accuracy for colorectal cancer, and adverse events with the 2 techniques.Eleven studies, including 4 randomized controlled trials (RCTs) with 1851 patients were included in the final analysis. A total of 1071 lesions were removed using U-EMR, and 1049 lesions were removed using C-EMR. Although U-EMR had an overall superior en-bloc resection rate compared with C-EMR (OR, 1.9; 95% confidence interval [CI], 1-3.5; P = .04), both techniques were comparable in terms of polyps >20 mm in size (OR, 0.8; 95% CI, 0.3-2.1; P = .75), R0 resection (OR, 3.1; 95% CI, 0.74-12.6; P = .14), piecemeal resection (OR, 3.1; 95% CI, 0.74-12.6; P = .13), and diagnostic accuracy for colorectal cancer (OR, 1.1; 95% CI, 0.6-1.8; P = .82). There were lower rates of polyp recurrence (OR, 0.3; 95% CI, 0.1-0.8; P = .01) and incomplete resection (OR, 0.4; 95% CI, 0.2-0.5; P = .001) with U-EMR. Both techniques have comparable resection times and safety profiles.Our results support the use of U-EMR over C-EMR for successful resection of colorectal lesions. Further randomized controlled trials are needed to evaluate the efficacy of U-EMR for resecting polyps >20 mm in size.