Technical tips and pitfalls of duodenal underwater endoscopic mucosal resection

With the recent advancement of endoscopic equipment and the increased awareness of endoscopists, the opportunity of detecting small duodenal epithelial tumors [superficial duodenal epithelial tumors (SDETs)] during screening has been increasing. In the duodenum which has a thin wall, preoperative biopsy can easily reveal severe fibrosis, and endoscopic mucosal resection (EMR) often cannot be performed because the lesion cannot be lifted up by submucosal injection. Recently, underwater EMR (UEMR), in which the lumen of the gastrointestinal tract is filled with water, instead of EMR with submucosal injection was reported. UEMR allows resection of even lesions with fibrosis. Moreover, the risk of intraoperative perforation is reported to be low. UEMR is expected to become a standard treatment for small-sized SDETs as a safe and reliable treatment.