Feasibility and outcomes of underwater endoscopic mucosal resection for ≥ 10 mm colorectal polyps

Background: Underwater endoscopic mucosal resection (UEMR) is an emerging strategy for the management of colorectal polyps. We aimed to evaluate the efficacy and safety of UEMR for clinically significant (≥ 10 mm) colorectal polyps. Methods: We performed a prospective dual-centre study of polyps ≥ 10 mm undergoing UEMR between June 2014 and March 2017. Outcomes measured comprised: (1) completeness of resection at index UEMR, (2) intraprocedural and 30-day complications, (3) rates and predictors of submucosal lift, en bloc resection, polyp/adenoma recurrence and (4) pain score. Endoscopy records were correlated with histology. Results: 85 patients underwent UEMR of 97 polyps. Resection was endoscopically complete at index UEMR in 97.9%. The median pain score was 0 (no pain). Submucosal lift was required in 29.9% and correlated with polyp size ≥ 30 mm (p = 0.03) and clip placement (p = 0.004). En bloc resection was achieved in 45.4%, and inversely correlated with polyp size ≥ 20 mm (p < 0.001). 30-day complications (4.1%) were minor and consisted of intraprocedural bleeding (n = 2) and delayed bleeding (n = 2). 60.8% attended endoscopy post-UEMR after a median interval of 6 months, with 20.3% polyp and 13.6% adenoma recurrence. Polyp recurrence was associated with piecemeal resection (p = 0.04), recurrent polyp (p = 0.02), female sex (p = 0.01) and poor access (p = 0.005). Predictors for adenoma recurrence included female gender (p = 0.01) and difficult access (p < 0.001). Recurrence rates did not differ with polyp size, site, morphology, dysplasia status, submucosal injection, patient age, or study centre. Conclusions: UEMR is an effective, safe and well tolerated option for significant colorectal polyps. Piecemeal resection, recurrent polyp, female gender, and difficult access are predictors of post-UEMR polyp recurrence.