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. 2026 Feb 14;6(1):e70294.
doi: 10.1002/deo2.70294. eCollection 2026 Apr.

Feasibility Study of Modified Underwater Endoscopic Mucosal Resection for Colorectal Polyps

Kaizo Kagemoto  1 , Koichi Okamoto  1 , Yoji Takeuchi  1   2 , Yasuyuki Okada  1 , Motoko Sei  1 , Shota Fujimoto  1 , Ryo Shinomiya  1 , Takeshi Mitsuhashi  1 , Takanori Yoshimoto  1 , Reiko Yokoyama  1 , Tomoyuki Kawaguchi  1 , Yoshifumi Kida  1 , Yasuhiro Mitsui  1 , Yutaka Kawano  1 , Masahiro Sogabe  1 , Hiroshi Miyamoto  1 , Yasushi Sato  1 , Tetsuji Takayama  1
Affiliations

Feasibility Study of Modified Underwater Endoscopic Mucosal Resection for Colorectal Polyps

Kaizo Kagemoto et al. DEN Open. .

Abstract

Objectives: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Keywords: UEMR; colorectal polyps; modified UEMR; submucosal tissue thickness; underwater.

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Conflict of interest statement

Author Tetsuji Takayama received a research grant from Fujifilm. Author Yoji Takeuchi is an Associate Editor of DEN Open: honoraria for lectures from Olympus, Fujifilm, Boston Scientific Japan, Daiichi‐Sankyo, Miyarisan Pharmaceutical, EA Pharma, Zeria Pharmaceutical, Viatris, Tsumura & CO, Kyorin Pharmaceutical, Otsuka Pharmaceutical Factory, Fuji Pharma Co, AI Medical Service, and Takeda Pharmaceuticals. The other authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Schematic diagrams of modified underwater endoscopic mucosal resection (M‐UEMR). (a) The target lesion was detected. (b, c) Water immersion and snaring the polyp underwater. (d) Infused water was suctioned and replaced with CO2 after snaring. (e) The polyp was resected by electrocautery.
FIGURE 2
FIGURE 2
Modified underwater endoscopic mucosal resection for a colorectal polyp. (a) White light imaging (WLI) showed a slightly elevated lesion (0‐IIa) in the transverse colon. (b, c) Narrow band imaging (NBI); underwater snaring of the polyp. (d) Removing the water and inflating with CO2 after snaring. (e) The wound had no residual lesion after resection. (f) Clipping with ease. (g) Hematoxylin and eosin (H&E) staining (orig. mag. × 10); a low‐grade adenoma with sufficient submucosal tissue.
See this image and copyright information in PMC

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