Underwater Endoscopic Mucosal Resection of Colorectal Neoplasia is Easily Learned, Efficacious, and Safe

Background: Underwater endoscopic mucosal resection (UEMR) without submucosal injection is a novel endoscopic procedure. It is not known if UEMR can be easily taught and learned, and the efficacy and safety of UEMR has not been demonstrated at multiple medical centers. Our aims were to demonstrate that (1) UEMR is a technique that can be easily learned by an endoscopist trained in traditional EMR, (2) endoscopic ultrasound (EUS) may not be required before UEMR, and (3) UEMR is an efficacious and safe method for resection of large or flat neoplastic colorectal lesions.

Methods: An experienced interventional endoscopist began performing UEMR after observing UEMR procedures. Colorectal UEMR was performed using a pediatric colonoscope with a cap, a waterjet, and a ‘duck-bill’ snare using blended current. Submucosal injection was not used. Patient data were collected prospectively.

Results: A total of 21 patients (17 men, mean age 64.9 years, range 51-83) referred for polypectomy of large colorectal lesions underwent UEMR. A total of 43 colorectal lesions with a mean size of 20 mm (range 8-50) were resected by UEMR. Lesions were found in the right colon (N = 16), transverse colon (N = 5), left colon (N = 19), and rectum (N = 3). Pathology demonstrated tubular adenoma (N = 29), tubulovillous adenoma (N = 5), high-grade dysplasia (N = 3), serrated sessile adenoma without dysplasia (N = 3), and non-neoplastic tissue (N = 3). EUS was used in only two cases of rectal neoplasia (4.7 %). Of the UEMRs, 97.7 % were successful with complete resection of colorectal polyps. The only adverse event was one case (2.3 %) of delayed post-UEMR bleeding.

Conclusions: UEMR was easily learned by an endoscopist already skilled in conventional EMR. EUS may not be required prior to most UEMR procedures. UEMR appears to be an efficacious and safe alternative to traditional EMR or ESD for large or flat colorectal neoplasms.