Feasibility Study of Modified Underwater Endoscopic Mucosal Resection for Colorectal Polyps

Underwater endoscopic mucosal resection (UEMR) is widely performed for colorectal tumors. However, in our experience, it is sometimes difficult to keep a clear endoscopic view underwater, due to dirty fluid inflow or insufficient water pooling after grasping the polyp, or bleeding just after endoscopic resection. To compensate for such challenges, we reported modified UEMR (M-UEMR) as a procedure for snaring underwater and undergas resection. Therefore, we conducted a prospective clinical trial to investigate the safety and efficacy of M-UEMR.

This single-center prospective study was conducted at Tokushima University Hospital. Patients with 10-25 mm colorectal polyps were enrolled. The polyps were snared underwater, then infused water was removed, and the lumen was inflated with CO₂ for resection, as described in our previous report. Measured outcomes were R0 resection rate and adverse events such as bleeding, perforation, and post-polypectomy syndrome. In addition, we evaluated the en bloc resection rate and thickness of submucosal (SM) tissue of the resected specimens.

Forty patients were enrolled, and the R0 resection rate was 80% (95% confidence interval [CI]: 64.4-90.9). No procedure-related adverse events were observed. En bloc resection was 92.5% (95% CI: 79.6-98.4). The median thickness of SM tissue (range) was 574 µm (241-2632) at the center of the specimen.

M-UEMR demonstrated a high R0 resection rate with a safe profile. M-UEMR is expected to be utilized as an alternative technique to UEMR for colorectal polyps in patients with difficulty maintaining a clear visual field.