Tip-fixing underwater endoscopic mucosal resection without submucosal injection for a laterally spreading colon polyp.

Background and Aims: Underwater endoscopic mucosal resection (EMR) has become a popular endoscopic resection method for intermediate-to-large colorectal polyps. However, the snare tip can sometimes slip when opening or closing the snare, resulting in increased risk of piecemeal resection. To address this issue, we report our technique of tip-fixing underwater EMR without submucosal injection for a laterally spreading colon polyp. Methods: Degassed water was infused using a mechanical water pump to completely fill the lumen. By projecting the tip of the snare by 2 mm, a mucosal incision was made on the oral side of the lesion using a cutting current. The snare was positioned appropriately around the lesion. After the lesion was captured, resection was performed using electrocautery. Results: Complete en bloc resection was achieved with no adverse events, and the mucosal defect was completely closed using clips. Pathological findings indicated a low-grade tubulovillous adenoma with negative margins. Conclusions: In previous tip-in EMR studies, a spot-shaped mucosal incision was created at the oral normal mucosa with prior submucosal injections using the snare tip to fix the snare. However, submucosal injection was not required in our technique of tip-fixing underwater EMR. Essentially, intraluminal water serves as a heat sink which, when combined with a relatively thicker wall resulting from the relaxation of mucosal tension by removing intraluminal air, may protect against thermal injury of the deeper colonic wall even while making a precut with the snare tip. However, excessive snare exposure, overapplication of cautery, or deep snare driving could cause perforation, especially in thin-walled areas such as the right-sided colon or small intestine.