The 6TGS technique is a novel direct endoscopy progression method, with no paradoxical movement involved.
Our team discovered the 6TGS technique during an STMF procedure. Through practice and after analyzing the results, the present study summarizes the operation method and the success rate of 6TGS. Unlike the typical progression way, in which the gastroscope’s tip usually reaches the antrum first, the 6TGS technique uses the resistance of the posterior wall of the upper gastric body (near the junction with the fundus) and the greater curvature as the supporting force to progress the gastroscope along the arc from the posterior wall of the gastric body to the angular incisure, making a “6”-turn along the gastric wall. This route allows the gastroscope to access the fundus of the stomach and even access just below the gastric cardia. The fundus of the stomach can then be handled from all angles. Thus, there is no need for paradoxical movement, making it much easier for the operators to access the lesion for more visualization and handling in operation. This novel endoscopy progression method is guaranteed to improve the STMF operation.
Additionally, when observing the fundus of the stomach using the 6TGS technique, it was found that the mucosa just below the gastric cardia can be clearly visualized. The gastroscope tip could operate the lesion at a close distance, which can significantly benefit operating on lesions below the gastric cardia.
6TGS: Solutions to the challenges of endoscopic treatment of GIST in the gastric fundus
The fundus of the stomach is considered a challenging area for ESD, ESE, or EFTR[18, 19]; the ESD technique is complex and prone to perforation, and the EFTR technique intentionally destroys the full thickness of the gastric wall, causing perforation to remove the lesion then sutures the wound by nylon suture and or hemostatic clips. One of the current endoscopic treatments used for STMF is EFTR. And indeed, EFTR surgery was predominant in our surgeries (5/7).
Endoscopic operation on gastric fundus is challenging, mainly due to the need for the traditional endoscopic progression method to be bent backward (U-turn) to access and observe the fundus of the stomach completely. The direction of endoscopy body movement is opposite to the direction of observation (paradoxical movement), and the endoscopy body gets suspended, which makes the operating space for the fundus of the stomach limited. When the endoscope’s body is suspended using the common U-turn technique, the forward injection force becomes immensely impaired, and the injection needle is perpendicular to the muscularis propria, making it difficult to find the submucosal space. Additionally, the resistance increases when surgical instruments (such as electrotome, thermal coagulation forceps, etc.) are delivered through the instrument channel due to the big curved angle. Following the current commonly used technique, we found that endoscopic treatment of STMF lesions in the middle of the fornix and anterior wall of the fornix was extremely challenging, especially the anterior wall of the fornix at the side of the greater curvature. Thus, a better endoscopic technique was needed to observe, deliver surgical instruments, and operate on these challenging tumor sites.
Operating Characteristics of the 6TGS
6TGS solves the problem of eliminating the need for paradoxical movement; thus, the gastroscope’s body becomes stable, contributing to more exposure of the lesion, improving the visualization, and increasing the forward puncture ability of the injection needle during submucosal injection.
Except for STMF in the posterior wall of the fundus, 6TGS allows the angle of the endoscope’s tip to reach the mucosa and muscle layer for submucosal injection, and a transverse incision can be used to cut the mucosa above the lesion, as each layer below the mucosa/above the lesion could be clearly observed. 6TGS ensures that the direction of the electrical cutting tool is parallel to the muscle during dissection, which reduces injury and the risk of bleeding.
Factors affecting 6TGS
The success rate of 6TGS was 70% in our clinical practice. At present, 6TGS could only be performed while patients were in the supine position and under general anesthesia with endotracheal intubation. The 6TGS failure in 3 cases may be related to the morphology of the gastric fundus. In all successful cases, less air volume in the stomach was required. More case studies are needed to investigate the factors influencing the success rate of 6TGS. The success rate of 6TGS may be related to the morphology of the fundus, the amount of air in the stomach, and the patient posture after general anesthesia, which requires further observation and study in the future. The present study has some limitations due to the small sample of STMF patients included who qualified for 6TGS; thus, bigger observational studies are needed to promote 6TGS in the future.