Effectiveness and safety of underwater techniques in gastrointestinal endoscopy: a comprehensive review of the literature

Background: Conventional endoscopic resection techniques such as endoscopic mucosal resection (EMR) or endoscopic submucosal dissection (ESD), represent the standard of care for treatment of superficial gastrointestinal lesions. In 2012 a novel technique called underwater endoscopic mucosal resection (U-EMR) was described by Binmoeller and colleagues. This substantial variation from the standard procedure was afterwards applied at endoscopic submucosal dissection (U-ESD) and recently proposed also for peroral endoscopic myotomy (U-POEM) and endoscopic full-thickness resection (U-EFTR).

Methods: This paper aims to perform a comprehensive review of the current literature related to supporting the underwater resection techniques with the aim to evaluate their safety and efficacy.

Results: Based on the current literature U-EMR appears to be feasible and safe. Comparison studies showed that U-EMR is associated with higher "en-bloc" and R0 resection rates for colonic lesions, but lower "en-bloc" and R0 resection rates for duodenal non-ampullary lesions, compared to standard EMR. In contrast to U-EMR, little evidence supporting U-ESD are currently available. A single comparison study on gastric lesions showed that U-ESD had shorter procedural times and allowed a similar "en-bloc" resection rates compared to standard ESD. No comparison studies between U-ESD and ESD are available for colonic lesions. Finally, only some anecdotal experiences have been reported for U-POEM or U-EFTR, and the feasibility and effectiveness of these techniques need to be further investigated.

Conclusions: Further prospective studies are necessary to better explore the advantages of underwater techniques compared to the respective standards of care, especially in the setting of U-ESD where consistent data are lacking and where standardization of the technique is needed.