Application of hydrogels as submucosal fluid cushions for endoscopic mucosal resection and submucosal dissection

Numerous new techniques have recently been reported and described for the endoscopic mucosal resection (EMR) of large superficial lesions of the gastrointestinal tract, using various natural, synthetic, and semi-synthetic materials such as chitin/chitosan and their derivatives. Although saline-assisted EMR is an established minimally invasive therapy, en bloc resection and histopathological analyses are required to determine its curative potential. In addition, complete resection of lesions of > 2 cm in diameter remains difficult, despite improved EMR techniques. The development of endoscopic submucosal dissection (ESD) has increased dissection rates for en bloc resection of large lesions, but perforation occurs more frequently during ESD than during EMR. Submucosal injections of those biomaterials which have high viscosity and hydrogelatinization ability as submucosal fluid cushions (SFC) may facilitate ESD as well as EMR for the treatment of superficial tumors of the alimentary tract. In this review, we describe the application of biomaterials such as chitosan derivatives, sodium hyaluronate, and 50 % glucose as a SFC for ESD, focusing photocrosslinked chitosan hydrogels (PCH) which we have originally developed.