Gas-alternating-water infusion method with/without internal traction assistance: a novel technique of endoscopic submucosal dissection for large colorectal tumors regardless of gravity direction

Introduction
Endoscopic submucosal dissection (ESD) using underwater technique has been developed to make colorectal ESD easier and safer. We have carried out a novel technique of colorectal ESD using gas-alternating-water infusion method for en-bloc resection of large colorectal tumors.

Aim
To evaluate the feasibility and safety of colorectal ESD using the gas-alternating-water infusion method (GAW-ESD) with or without internal traction assistance depending on the level of exposure of the submucosal space, for large colorectal tumors (≥ 3 cm in size).

Material and methods
All 8 patients were kept in the left lateral position during GAW-ESD as follows: (1) C-shaped mucosal incision. (2) The colorectal lumen was instilled with normal saline. Then the mucosal flap on the lower side of gravity was created with the help of buoyancy, followed by a V-shaped dissection both below and above the liquid surface, if necessary, assisted by internal traction using one-matching-many repositionable clips attached to one rubber band. (3) The post-ESD defect was closed underwater using repositionable clips.

Results
GAW-ESD was performed successfully in eight patients, five without internal traction, three with internal traction. The en-bloc resection rate was 100%. No perforation occurred. Only one patient suffered from post-ESD bleeding, which was resolved by endoscopic clipping.

Conclusions
GAW-ESD with/without internal traction is safe and effective for en-bloc resection of large colorectal tumors, with the advantages of quick gas/liquid switch, stable platform, fixed position, buoyancy effect, counteraction design, dissection acceleration, heat-sink effect, optical zoom effect, and downsizing effect.