Norio Fukami, MD, AGAF, FACG, FASGE
The anatomy of the esophagus is rather straightforward, with its tubular and fixed structure surrounded by soft tissue (adventitia and mediastinum), respiratory system (trachea and lung/pleura), and vascular system. The layered structure of the esophageal wall is similar to that of the rest of the gastrointestinal (GI) tract. However, it is important to highlight that the stratified squamous cell mucosal layer in the esophagus is thinner than the columnar-lined epithelium in the rest of the GI tract. The submucosal layer in the esophagus can be easily expanded with a lifting solution, which facilitates subsequent mucosal incision and submucosal dissection.
When performing endoscopic submucosal dissection (ESD), there are considerable technical differences between the resection approach for squamous cell neoplasia (SCN) and that for Barrettrelated neoplasia (BE-N). In this chapter, we will illustrate the basic techniques of esophageal ESD, focusing on differences when resecting SCN and BE-N.
Consideration for Esophageal Endoscopic Submucosal Dissection
The esophagus is a tubular, relatively small-caliber, fixed intestinal organ. The esophageal wall is characterized by a thin muscularis propria without a covering serosal layer but rather only with adventitia. Given these anatomical features, adverse events, including leakage after muscularis propria injury with ESD, are high. Endoscope maneuvers during resection are performed by subtle push and pull, angle manipulation, and precise rotation. Excessive rotational movement for incision can result in inadvertent muscularis propria or deep injury and should be avoided.
Determining the width, length, and location of resection by advanced imaging and by thermal marking are crucial preprocedural steps to help plan the most appropriate resection method strategy. Resection can potentially involve less than one-half or the entire circumference. In either case, the initial mucosal incision should start at the distal aspect of the resection margin and the incision to be made to the middle of the submucosal layer. This is important to avoid overshooting during submucosal dissection or tunneling, as submucosal dissection tends to go beyond the distal end of the lesion without a visible end point. Additionally, attempt of mucosal incision at distal margin after completing a fair amount of proximal dissection can be extremely challenging because of a visual obstruction from the dissected mucosal flap. Furthermore, longitudinal mucosal incision tends to be more difficult at lower points of gravity because of pooling of injection fluid, irrigating water, or blood. Hence, incising this side of the mucosa early in the course of the ESD is highly advisable.
As previously mentioned, there are 2 major resection methods available in the esophagus: (1) the conventional method (full marginal incision followed by submucosal dissection)1,2 (Figure 19-1) and (2) the tunneling method.3–6 The conventional approach can be used for all lesions and is the treatment of choice for smaller lesions for which tunneling can be challenging.
In patients with Barrett’s neoplasia, the mucosa can be unexpectedly thick, which often necessitates a deeper initial incision to reach the submucosal layer. This can be challenging, particularly for beginners, as discerning the different layers in this situation can be difficult and the risk of injury to the muscularis propria or perforation is high at the time of initial mucosal incision. Careful mucosal incision may expose the muscularis mucosae, with the submucosal layer found deeper to this layer after careful ongoing dissection (Figure 19-2).
Popular ESD electrocautery knives for esophageal ESD include the HookKnife, DualKnife, ITKnife-nano (Olympus), and FlushKnife (Fujifilm). Scissors-type knives can also be utilized as well where suitable. In Western countries, the HybridKnife (Erbe) is also available with its unique capability of needleless injection. The only drawback of the HybridKnife is its thicker needle tip, which results in more coagulation effect with cutting. The injection capability within an ESD knife is highly desirable for quicker and safer ESD and will likely be incorporated into most knives in the future. The HookKnife is unique as it allows dissection with a hook-(pull)-and-cut technique resulting in increased safety, and it offers effective clean cutting without excessive cautery effect.1,3 The HookKnife is particularly advantageous in the setting of fibrosis and is often the author’s choice for SCN-targeted ESD. Details of the tools are described in a separate chapter in this book.
Steps of Endoscopic Submucosal Dissection
First, delineation of the target lesion should be performed by placing cautery marks around the margins of the lesion. Markings are recommended at about 5 mm outside the suggested neoplasm margin to ensure a negative pathological margin and mucosal incision is to occur just outside of the markings. The markings can be performed with noninsulated ESD knives (eg, Dual, Hook, Flush knives). Conversely, if an insulated knife is chosen for ESD (eg, ITKnife-nano), then an additional knife or argon plasma coagulation (Erbe) is required for this initial step. A strong cautery effect of markings tends to breach the squamous mucosa down to the submucosa, which often results in fluid leakage during submucosal injection. Hence, markings should be performed with soft coagulation or a very short burst of coagulation current to avoid mucosal break. Barrett’s mucosa is relatively resilient to the cautery effect but same precaution should be applied (Figure 19-3).
Long-lasting fluid should be injected into the submucosal layer just at or outside the markings. The mucosal incision is to be performed at or around the peak of the mound (lifted mucosa) and thus injection should be planned accordingly. For maximal lift, an endoscopist should instruct the assistant to forcefully inject 1 to 2 mL of fluid at a time, which facilitates the formation of a bleb confirming an adequate lift. The absence and inadequacy of a lift following an injection indicate that the tip of the needle may be too deep and not in the proper submucosal space rather than a true nonlifting sign. The first step would be to readjust the depth of the needle tip and reattempt injection.
Submucosal injection should proceed around the markings, connecting the blebs, in the region you plan to incise. Even though prolonged submucosal lift can be achieved with the injection of a long-lasting fluid, injection should be limited to the area where you plan to incise right after. Repeat injections should be performed when the lift is inadequate or not ideal. One cannot stress enough that an initial mucosal incision with inadequate lifting is a great risk for inadvertent muscularis propria injury or perforation. Often, injections can leave a “valley” or dip between the peaks of lifted mucosa. Submucosal lift is often inadequate at this site and repeated injection to eradicate the “valley” is necessary prior to dissection (Figures 19-4A and B). As previously mentioned, deep injection beyond the muscularis propria layer results in an appearance of a mild-moderate lift with an “inadequate lift” of the submucosal layer mimicking a nonlifting sign. An inadequate lift due to erroneous positioning of the tip of the needle or due to actual dense submucosal fibrosis can predispose to muscularis propria layer injury or perforation. An effort should be placed to seeing steep elevation of the mucosa, a sign of submucosal expansion, after each injection prior to mucosal incision.
Esophageal mucosal incision is usually started at the distal end of the lesion. The initial incision should be performed slowly and carefully in increments until the submucosal layer is exposed (Figures 19-5A through C). The muscularis mucosae are often visible during the initial incision, and this must be traversed to reach the submucosa. To direct the incision in the horizontal axis, the endoscope can be rotated with slight adjustments to the scope tip angle. Long uninterrupted mucosal incision rotating the endoscope should be avoided, as this increases the risk of inadvertent injury and perforation of the muscularis propria layer. Once the mucosal incision has been completed along the circumference at the distal end of the lesion, the next step depends on the method you plan to use.