Underwater endoscopic submucosal dissection with an insulated tip knife using diluted saline

Owing to buoyancy, underwater endoscopic submucosal dissection (ESD) offers improved visibility of the submucosal layer.¹ Previous research has demonstrated the effectiveness and speed of employing an insulated tip (IT) knife for ESD.^{2, 3} However, due to the current flow in the surrounding saline, employing large electrode devices such as an IT knife becomes challenging. Distilled water without electrolytes does not provide effective submucosal dissection. To address this, we utilized diluted saline (1:2 mixture of saline and distilled water) to modulate electrical flow via impedance difference (Fig. 1). We used this solution for underwater ESD, avoiding dimethicone to maintain transparency. Moreover, indigo carmine and undiluted hyaluronic acid were added to the local injection to aid visibility and protect the submucosal hyaluronic acid. There were three male cases and one female case, with three lesions in the stomach and one lesion in the colon. The average age was 79.2 years, the average resection time was 55 min, the average volume of flooding solution used was 1600 mL, and the average diameter of the lesions was 23.5 mm. We used an ITknife2 and ITknife nano (Olympus, Tokyo, Japan). A VIO-300D (Erbe Elektromedizin, Tubingen, Germany) was employed as a high-frequency surgical device. While there was no significant change in lesion elevation when using diluted saline compared to normal saline as the flooding solution, current leakage into the surrounding liquid was reduced, allowing for submucosal dissection. In underwater ESD, suctioning air to maintain a clear view is crucial. The reduction in current leakage into the surrounding flooded solution decreased the bubbles generated during submucosal dissection. Consequently, less effort was required to suction bubbles to maintain a clear view (Video S1). No incidents of postbleeding or perforation were observed. The use of diluted saline has expanded the options for underwater ESD devices.

Authors declare no conflict of interest for this article.