Virtual scale endoscope-assisted wide-field resection of large sessile serrated lesions

Large sessile serrated lesions (SSLs) are associated with a very high risk of incomplete resection. The CARE study found almost 50% incomplete resections among 10 to 20-mm SSLs [1]. Wide-field cold snare resection with submucosal injection (cap-assisted endoscopic mucosal resection, C-EMR) has been proposed as an effective method to prevent incomplete resection since distinguishing SSL margins during resection is difficult [2– 4]. In contrast to a hot snare, a more extended resection field is recommended for a cold snare [5]. However, quantification of the resection field extent in comparison to polyp size has been challenging in the past. The novel virtual scale endoscope (VSE; SCALE EYE, Fujifilm, Tokyo, Japan) can be used as dedicated technology to measure polyp size before resection and to ensure adequate postresection defect size. The VSE allows polyp size measurement during live colonoscopies by emitting a laser beam onto the mucosa to measure distance. This permits superimposition of a linear/circular ruler that changes in size depending on distance of the endoscope to the laser point (▶Fig. 1). We present VSE-assisted C-EMR for two large SSLs (▶Video 1). The polyps were assessed with the VSE before and after submucosal injection and resection to ensure adequate wide-field resection. SSLs were initially measured using the VSE and assessed using computer-aided diagnosis (CADx) to determine their size (> 10mm) and ensure that C-EMR was the adequate approach. Then the extent of wide-field resection was planned and controlled using the VSE. For resection, submucosal injection was used to allow better exposure of the entire polyp and obtain a pre-resection measurement using the VSE (▶Fig. 2). The polyps were then resected, and an artificial-intelligence system (CADx) was used to detect polyp remnants at the margins during CEMR (▶Fig. 3). The resection extent was adjusted based on CADx and VSE information to ensure adequate and complete wide-field resection. The final resection defect size wasmeasured to ensure that it was significantly larger than the pre-resection polyp size after submucosal injection (▶Fig. 4).