Underwater endosonography (uEUS) for enhancement of small mucosal and submucosal gastrointestinal lesions.

Water immersion of gastrointestinal (GI) mucosal lesions is a reliable method to ensure the safety and completeness of resection without the need for a submucosal fluid cushion [1]. Further, this method may improve endoscopic optics by providing a magnification effect of the mucosa [2]. We hypothesize that gas decompression and water exchange have several advantages to endoscopic ultrasound (EUS): it liberates ultrasound wave propagation, decreases artifacts, and provides enhanced EUS views. It also minimizes GI lumen accordioning, with an approximation of folds that may be conducive to more versatile exam and EUS-guided interventions [3]. These characteristics are advantageous especially when attempting to visualize and sample small mucosal and submucosal lesions. In this exposition, we present several diagnostic EUS cases of small (< 15 mm) GI luminal lesions facilitated by underwater EUS (uEUS) for accurate characterization and sampling acquisition.