Figure 1.

A, A superficial 50-mm mass located in the second portion of the duodenum. B, The mass is dissected by endoscopic submucosal dissection (ESD) using the pocket-creation method. C, Mucosal defect after ESD, measuring approximately 60 mm. D, The margins of the mucosal defect are firmly grasped underwater with reopenable clips. Where the edges of both submucosal defects were invisible, the clips were reopened and used to grasp the edges. E, After confirmation that the edge of the submucosa was completely grasped using the reopenable clips, clips were deployed. F, A large mucosal defect remained in the center of the resection site after the edges of the mucosal defect were approximated with a reopenable clip. G, The thread-assisted mucosal defect closure technique was used; the edges of the mucosal defect are gradually approximated and closed securely using a reopenable clip. H, The mucosal defect is completely closed using underwater reopenable clip closure (U-REC). I, Four days after the duodenal ESD with complete closure of the mucosal defect using U-REC, all clips remained in place.