Tufts University School of Medicine

Erik Holzwanger

Endoscopic submucosal dissection (ESD) has long been utilized in eastern countries, with its origins tracing back to Japan. It was borne out of necessity in the treatment of early gastric cancers, where endoscopic mucosal resection (EMR) fell short, and surgery was the only curative option. It allows for en bloc resection of larger lesions using electrocautery knives. In contrast, EMR may be functionally limited by snare diameter and piecemeal resection, thus carrying a higher risk of incomplete resection and local recurrence. The critical threshold for en bloc resection, especially important for malignant or potentially malignant lesions, occurs at approximately 3cm.

ESD is presently applied to lesions throughout the GI tract using the same general framework. First, the mucosa is carefully inspected using both high-definition white-light endoscopy and narrow-band imaging (NBI) to identify the extent of the lesion. The margins are then marked using thermal energy with the electrocautery knife. A submucosal lift is created with an injection of fluids ranging from saline mixed with methylene blue to proprietary gel solutions. Electrocautery is then used to enter the submucosa at the site of the previous injection, creating a mucosal flap. From here, the process is repeated until the area is resected. There are multiple methods for closure, ranging from mechanical devices such as clips to topical agents to promote healing and prevent bleeding. Multiple society criteria exist for defining a curative resection, which could previously only be obtained with surgical interventions.

“Future devices in development seek to deploy robotics, similar to laparoscopic surgery, to improve dexterity and control of resection”

The basic equipment used in ESD is fairly standardized. Most clinicians utilize a transparent cap for improved visualization while working in the submucosal space, an ESD-knife, and some type of coagulation device to control intraprocedural bleeding. The development of ESD and its expanding application has spurred the creation of new tools and devices to address specific challenges.

There is no shortage of knife options for these procedures. The knives vary mainly by their tip and the presence (hybrid) or absence of injection capabilities. Many modern ESD-knives utilize hybrid technology such that the endoscopist can deliver submucosal injection through the knife itself, without having to change tools, which provides an advantage with respect to procedure time. Many endoscopists will develop their own preference for knife shape. They may be needle-shaped, ball-shaped, star-shaped, or ceramic-capped. The different shapes offer varying degrees of control and ability to selectively cut fibers. Ceramic or insulated caps knives may serve a dual purpose for hemostasis as well. In certain situations, the endoscopist may even choose a scissor-type device, which allows them to grasp tissue and manipulate/confirm planes prior to cutting.

Much of the challenge of ESD comes down to the lack of manual traction, as the free edge(s) of the lesion are left at the mercy of gravity. This can impair visualization and make it difficult to distinguish the submucosal plane, especially with fibrotic lesions. Early adaptations deployed through-the-scope clips onto the lesion with nylon suture, dental floss, or a rubber band to allow the endoscopist to either pull or push the free edge. While these are low barrier adaptations, they only apply traction in one direction and are difficult to manipulate. They are, however, the most used forms of traction. This has been followed by distal attachments such as Endolifter, where a clear cap outfitted with forceps is attached to the end of the scope. These forceps can be used by the endoscopist to push, pull, or lift.

Boston Scientific has developed a more robust device called the ORISE tissue retraction system involving an overtube equipped with a distal “cage” to spread the tissue and two independent graspers with distal articulation for the application of traction. The last category of traction devices is through the scope options. One novel example of an articulation device is called TRACMOTION. These require a double channel endoscope and provide a broad array of grasping and traction angles plus locking options without being limited by distal attachments or overtubes. Future devices in development seek to deploy robotics, similar to laparoscopic surgery, to improve dexterity and control of resection.

The future of ESD is bright, marked by ever expanding capabilities, and continues to evolve at rapid paces. With each challenge, the tools and techniques are adapted to push the boundaries further. At its core, ESD serves as a non-surgical option for certain GI malignancies, the list of which continues to expand.