Underwater endoscopic mucosal resection is associated with fewer recurrences and earlier curative resections compared to conventional endoscopic mucosal resection for large colorectal polyps

Background Studies comparing the efficacy and safety of conventional saline-assisted piecemeal endoscopic mucosal resection (EMR) to underwater EMR (UEMR) without submucosal lifting of colorectal polyps are lacking. The objective of this study was to compare the efficacy and safety of EMR to UEMR of large colorectal polyps. Methods Two hundred eighty-nine colorectal polyps were removed by a single endoscopist from 7/2007 to 2/2015 using EMR or UEMR. 135 polyps (EMR: 62, UEMR: 73) that measured ≥15 mm and had not undergone prior attempted polypectomy were evaluated for rates of complete macroscopic resection and adverse events. 101 of these polyps (EMR: 46, UEMR: 55) had at least 1 follow-up colonoscopy and were studied for rates of recurrence and the number of procedures required to achieve curative resection. Results The rate of complete macroscopic resection was higher following UEMR compared to EMR (98.6 vs. 87.1%, p = 0.012). UEMR had a lower recurrence rate at the first follow-up colonoscopy compared to EMR (7.3 vs. 28.3%, OR 5.0 for post-EMR recurrence, 95% CI: [1.5, 16.5], p = 0.008). UEMR required fewer procedures to reach curative resection than EMR (mean of 1.0 vs. 1.3, p = 0.002). There was no significant difference in rates of adverse events. Conclusions UEMR appears superior to EMR for the removal of large colorectal polyps in terms of rates of complete macroscopic resection and recurrent (or residual) abnormal tissue. Compared to conventional EMR, UEMR may offer increased procedural effectiveness without compromising safety in the removal of large colorectal polyps without prior attempted resection.