Comparison of Underwater vs Conventional Endoscopic Mucosal Resection of Intermediate-size Colorectal Polyps

Abstract Background & Aims Endoscopic mucosal resection (EMR) with submucosal injection is an established method for removing colorectal polyps, although the en bloc resection rate decreases when polyp size exceeds 10 mm. Piecemeal resection increases local recurrence. Underwater EMR (UEMR) is an effective technique for removal of sessile colorectal polyps and we investigated whether it is superior to conventional EMR (CEMR). Methods We conducted a multicenter randomized controlled trial at 5 institutions in Japan. Patients with endoscopically diagnosed, intermediate size (10–20 mm) sessile colorectal lesions were randomly assigned to undergo UEMR or CEMR. Only the most proximal lesion was registered. The UEMR procedure included immersion of the entire lumen in water and snare resection of the lesion without submucosal injection of normal saline. We analyzed outcomes of 108 colorectal lesions in the UEMR group and 102 lesions in the CEMR group. R0 resection was defined as en bloc resection with a histologically confirmed negative resection margin. The primary endpoint was the difference in the R0 resection rates between groups. Results The proportions of R0 resections were 69% (95% CI, 59%–77%) in the UEMR group vs 50% (95% CI, 40%–60%) in the CEMR group ( P = .011). The proportions of en bloc resections were 89% (95% CI, 81%–94% in the UEMR group vs 75% (95% CI, 65%–83%) in the CEMR group ( P = .007). There was no significant difference in median procedure time (165 sec vs 175 sec) or proportions of patients with adverse events (2.8% in the UEMR group vs 2.0% in the CEMR group). Conclusions In a multicenter randomized controlled trial, we found that UEMR significantly increased the proportions of R0 resections for 10–20-mm sessile colorectal lesions without increasing adverse events or procedure time. Use of this procedure should be encouraged. Trials registry number: UMIN000018989