Comparison of the resection depth between endoscopic mucosal resection and underwater endoscopic mucosal resection for superficial non-ampullary duodenal epithelial tumors: A retrospective study

ObjectivesThere is concern that underwater endoscopic mucosal resection (UWEMR) uses buoyancy to elevate the lesion for snare resection, resulting in a shallower resection depth than that in endoscopic mucosal resection (EMR). We aimed to compare conventional EMR and UWEMR in terms of resection depth.MethodsWe retrospectively reviewed cases in which EMR or UWEMR was performed for superficial non-ampullary duodenal epithelial tumors of <= 20 mm between April 2018 and February 2024. The endpoints were histological complete resection rate, en bloc resection rate, presence of muscularis mucosa and submucosa in the resection specimen, and submucosal index calculated from the resection specimen.ResultsEMR was performed on 19 lesions and UWEMR was performed on 52 lesions. Histological complete and en bloc resection rates were not significantly different between EMR and UWEMR (57.9% and 63.5%, respectively, p = 0.78; 78.9% and 90.4%, respectively, p = 0.24). No significant differences were observed between EMR and UWEMR in the muscularis mucosa of the resected specimens (78.9% and 92.3%, respectively, p = 0.20). The presence of submucosa in resected specimens was encountered less often in EMR cases than in UWEMR cases (57.9% versus [vs.] 84.6%, p = 0.03). There were significant differences in the submucosal index in the resected specimens between EMR and UWEMR cases (median 0.15 [interquartile range 0-0.39] vs. 0.33 [0.17-0.57], p = 0.04).ConclusionUWEMR potentially includes the submucosa within the specimen.