Fig. 4.

Schematic illustration of the water pressure method to facilitate endoscopic submucosal dissection of a lesion located on the gravitational side. a Under conventional gas insufflation, the mucosal flap collapses due to the gravity, leaving insufficient submucosal operation space. b With the water pressure method, buoyancy makes the mucosal flap float up against gravity, while active water pressure via water-jet of endoscope is utilized as a complement to lift the mucosal flap that expands submucosal space.