Clinical Outcomes of Partial Injection Underwater Endoscopic Mucosal Resection for Superficial Non‐ampullary Duodenal Epithelial Tumors (With Video)

Objectives Although endoscopic resection is widely performed for superficial non‐ampullary duodenal epithelial tumors (SNADETs), conventional endoscopic mucosal resection (CEMR) may be associated with suboptimal complete resection rates. Partial injection underwater EMR (PI‐UEMR) has been proposed to improve the visualization of distal lesion margins and facilitate en bloc resection. We aimed to evaluate the outcomes of PI‐UEMR for SNADETs, using CEMR as a historical institutional comparator. Methods This single‐center observational cohort study included patients who underwent endoscopic mucosal resection for SNADETs between September 2015 and December 2025. Lesions treated with CEMR or PI‐UEMR were analyzed. The primary outcomes were en bloc and R0 resection rates. The secondary outcomes included histological diagnosis and procedure‐related adverse events, including intraoperative perforation, delayed perforation, and delayed bleeding. Results In total, 77 lesions in 73 patients were analyzed, including 39 treated with CEMR and 38 treated with PI‐UEMR. The en bloc resection rates were 90.0% and 97.4% in the CEMR and PI‐UEMR groups, respectively. The R0 resection rate was significantly higher in the PI‐UEMR group than in the CEMR group (89.4% vs. 69.2%). Histological diagnoses were similar between the groups. No intraoperative perforation occurred in either group. No procedure‐related adverse events, including delayed perforation or bleeding, were observed in the PI‐UEMR group. Conclusions While maintaining a favorable safety profile, PI‐UEMR was associated with a higher R0 resection rate than CEMR in this study. It may represent an effective endoscopic treatment option for SNADETs, particularly when precise visualization of the distal lesion margins is required.