Underwater endoscopic mucosal resection of adenomas and colorectal serrated lesions: a prospective clinical study

BACKGROUND: Underwater endoscopic mucosal resection (UEMR) without submucosal injection has been described as an alternative technique to the endoscopic resection of adenomas and colorectal serrated lesions. We aimed to assess the feasibility, safety, and efficacy of UEMR in a Brazilian setting. METHODS: This was a prospective observational study of consecutive patients who underwent UEMR between January and July 2019, in a single tertiary care center. Inclusion criteria were lesions without endoscopic stigmata of deep submucosal invasion in patients referred for endoscopic resection of colorectal adenomas, and serrated lesions detected in a previous colonoscopy. The following features were assessed: complete resection rate, en bloc resection rate, resection time, adverse events, and resection infeasibility. RESULTS: A total of 36 patients underwent UEMR for 51 colorectal lesions. The mean/median lesion size was 16.24/13 mm and the mean/median resection time was 16.97/9.19 min. Histopathology revealed the following: tubular adenoma (43.1%), tubulovillous adenoma (13.7%), serrated lesions (41.2%), and intramucosal adenocarcinoma (2%). Complete resection was achieved in 86.3% of cases; 52.9% of the lesions were removed en bloc, while 47.1% were resected in a piecemeal fashion. UEMR was feasible in 96.1% of cases and failed on 2 occasions, requiring conversion to standard endoscopic mucosal resection. Minor intraoperative bleeding occurred in 5 patients (9.8%) and only 1 presented with delayed bleeding (2%), all controlled endoscopically. CONCLUSION: UEMR for removal of adenomas and colorectal serrated lesions was demonstrated to be feasible, safe and effective.