LAUSR

Underwater endoscopic mucosal resection (UEMR) is rapidly gaining popularity as a treatment that is easier than conventional EMR and endoscopic submucosal dissection (ESD) because submucosal injection is not necessary owing to the floating effect of tissue under water [1, 2]. However, it is currently unclear whether UEMR can ensure deep enough margins for pathological evaluation of earlystage colorectal cancer [3]. We present a case of modified UEMR with submucosal injection after underwater conditions have been established (UIEMR). The patient was a 33-year-old woman with a 12mm lesion in the sigmoid colon. On magnifying endoscopy with narrowband imaging, the lesion was diagnosed as type 2B by Japan NBI Expert Team classification (▶Fig. 1) [4]. After indigo carmine dye spray, the lesion showed a well-defined depressed area with central elevation (▶Fig. 2). The diagnosis was a nonpolypoid lesion and macroscopic appearance was Paris type 0-IIa + IIc. Magnifying endoscopy with crystal violet staining showed type Vı (noninvasive) pit pattern (▶Fig. 3). Additional endocytoscopic observation showed the disordered arrangement of the stained nuclei as EC 3a (▶Fig. 4) [5]. Endoscopic diagnosis was an intramucosal to submucosal superficial carcinoma (high grade dysplasia in Western descriptions). We performed UIEMR to achieve R0 resection (▶Video 1). UIEMR is UEMR plus submucosal injection as in conventional EMR. In UIEMR, the enE-Videos