Hiroyuki Aihara, MD, PhD, FACG, FASGE
Endoscopic submucosal dissection (ESD) allows for en bloc resection of large superficial neoplastic lesions. Colorectal ESD is technically demanding because of the thinner wall and anatomical complexity of the colon, the restricted mobility of the endoscope, and the loose submucosal tissue matrix preventing sustainable submucosal lifting. Colorectal ESD was first reported in 2003 by Yamamoto et al1 as a case report describing the successful removal of a large flat colon polyp, but it was not until 2012 that a billing code for ESD was finally approved in Japan, partially because of the higher risk of complications. It should be emphasized that the above-mentioned, organ-specific factors related to difficulties in colorectal ESD need to be fully understood before starting this procedure.
Colorectal Endoscopic Submucosal Dissection Knives and Technique
The currently commercially available electrosurgical knives in the United States for colorectal ESD (as of February 2019) are listed in Figure 21-1. When compared to commonly used knives for gastric ESD, the colorectal ESD knives are shorter and smaller to minimize the risk of inadvertent muscle injury. The ESD knives are broadly classified into 3 types based on their shape: noninsulated, insulated, and scissors-type.
Noninsulated Needle-Type Knife
Needle-type knives allow for fine and precise cutting and dissection based on their sharp active blades. In the United States, only the FlushKnife (Fujifilm) and HybridKnife (Erbe) are currently equipped with an injection function, whereas the DualKnife J and HookKnife (both Olympus) with injection capability has been available in Japan since 2015. This injection capability can be useful in eliminating the time necessary for device exchange and thus minimizing dissipation of the submucosal lift.
The first step of the mucosal incision with these needle-type knives is to make a small incision that penetrates the muscularis mucosa, confirmed by visualization of the dye-stained (eg, methylene blue, indigo carmine) submucosal tissue (Figures 21-2A and B). After reaching the submucosal tissue, the incision is broadened laterally to facilitate subsequent scope entry but not too large as to prevent dissipation of the injected fluid within the submucosa.
After the initial incision, the exposed submucosal tissue is further dissected by tracing the initial mucosal incision line. This is continued until the submucosal layer is expanded so the scope tip can enter the submucosal space. During submucosal dissection, the knife needs to be maneuvered in a parallel fashion to the muscle layer (Figure 21-2C) or toward the lumen side (Figure 21-2D) so the needle tip is directed away from the muscle. Maneuvers that pull the needle knife from the distal to proximal side should be strictly avoided unless this is the only way to dissect the tissue. This maneuver often results in muscle injury, since the tip of the knife is being directed perpendicularly toward the muscle layer.
The ITKnife-nano (Olympus) has a small ceramic ball tip, a metallic disc at the base of the ceramic ball, and a needle knife shaft. Effective incision and dissection can be performed with the blade of the knife and the metallic disc, while the ceramic ball tip protects the muscle layer from inadvertent injury from the distal end of the knife. Although this knife has a higher hemostatic effect compared to needle knives because of its wider surface area, more tension and higher wattage are usually required for effective incision and dissection.
After an initial small mucosal incision with a needle-type knife, the ceramic ball is inserted into the submucosal layer. The knife is pulled back to start the mucosal incision (Figure 21-3A). The knife angle becomes perpendicular to the muscle layer as it is pulled back; however, the insulated-tip protects the muscle layer from thermal injury.
In contrast to the ITKnife2 dissection technique in gastric ESD, blind submucosal dissection should be avoided in colorectal ESD. All dissection should be performed under direct vision of the target tissue (Figure 21-3B). This is because of the thinner muscle layer in the colon and rectum as compared with the stomach. Even minimal, transient contact with the active blade can result in colonic perforation.