Supplementary Material for: A Case of Duodenal Tumor Adjacent to the Diverticulum That Was Resected by the Technique of Partial Submucosal Injection Combined with Underwater Endoscopic Mucosal Resection

A 66-year-old male was referred to our hospital for treatment of duodenal tumor. The most difficult part was that the lesion was adjacent to duodenal diverticulum. Endoscopic mucosal resection (EMR) was difficult because submucosal injection spread broadly and quickly and makes it difficult to visualize the diverticulum edge of the lesion. Simple underwater EMR (UEMR) had risk for perforation at the diverticulum part because duodenal diverticulum is spurious diverticulum that defects the proper muscle layer. Therefore, to make sufficient distance between diverticulum and the lesion, we performed partial submucosal injection into only the diverticulum side of the lesion combined with simple UEMR. The lesion was resected en bloc without any adverse events. Histopathological diagnosis was tubular adenoma with moderate atypia and surgical margin negative. Partial submucosal injection combined with simple UEMR might be useful for duodenal tumor that has any technical difficulties as in this case.