Underwater endoscopy and resection

By keeping the colon more collapsed, water submersion keeps the sigmoid colon straighter, reduces looping during advancement, and limits elongation of the colon that occurs with gas distension. These advantages may be useful during intubation of a “difficult colon,” but broader benefits exist when water submersion is applied as a standard approach to colonoscopy. In contrast to gas insufflation, water submersion actually enhances the diagnostic and therapeutic efficacy of colonoscopy while causing less physical duress to the patient. Multiple randomized controlled trials comparing gas insufflation and water exchange technique have shown that water exchange decreases sedation needs, improves patient comfort, and enhances adenoma detection rates. For diagnosis, water submersion has an optical “zoom” effect that magnifies the mucosal architecture. This is further amplified by narrow band imaging (NBI). Therapeutically, water submersion enables endoscopic mucosal resection of neoplastic lesions without the need for submucosal injection. Using conventional EMR technique with gas insufflation the bowel wall is substantially thinned; submucosal injection is performed to reduce the risks of accidental ensnarement of or incision into the muscularis propria and transmural thermal injury that can lead to perforation. The technique of underwater EMR (UEMR) replaces gas with water and eliminates the need for submucosal injection. This technique was inspired by the author’s observation during EUS that, when filled with water, the muscularis propria retains its native thickness and circular configuration. The “folds” of a nondistended bowel consist of involutions of the mucosa and submucosa, analogous to the rugae of the stomach. Water immersion also “floats” a mucosal lesion away from the deeper wall layers. The treatment of bleeding under water immersion has been found to facilitate the identification of the precise origin of bleeding. Electrosurgical applications immersed in liquid are common in other surgical fields such as urology, arthroscopy, and ophthalmology and equally applicable to the gastrointestinal tract. A “heat sink” effect of water immersion may reduce the risk of transmural burn and other collateral damage to adjacent tissue. UEMR has been shown in multiple randomized controlled trials to achieve higher rates of en-bloc resection with no difference in complication rates and trends favoring reduced rates of lesion recurrence compared to conventional EMR technique using gas insufflation.