Hon Chi Yip, MBChB, FRCSEd and Philip W.Y. Chiu, MD, MBChB, FRCSEd, FRCSEd (Gen), FCSHK, FHKAM
Endoscopic submucosal dissection (ESD) was first developed in the 2000s for treatment of early gastric neoplasms.1 Since then, multiple large, published series have confirmed the efficacy of this technique in achieving en bloc curative resection with a low recurrence rate and excellent long-term survival.2–5 ESD has evolved as the standard of care for patients with early gastric cancers within the criteria of endoscopic resection. The indication and definition of curative endoscopic resection has been covered elsewhere in this book. This chapter will focus on different techniques of ESD in the stomach.
Patient Preparation and Positioning
Patients should be adequately fasted before the procedure. Thirty minutes before the start of the procedure, a mixture of mucolytics and defoaming agents such as simethicone, N-acetylcysteine or Pronase (Roche Applied Science) would be prescribed orally to optimize the view within the stomach. ESD in the stomach can be performed under conscious sedation or and general anesthesia. The decision on the type of anesthesia would depend both on the patient and procedural factors. ESD with an anticipated long procedural time (> 1 hour) and in a difficult position such as at the cardia where it is more affected by the patient’s respiratory pattern is better managed under general anesthesia. The standard left lateral position is usually sufficient for most ESD procedures in the stomach. Antispasmodic agents such as Hyoscine can be given during the procedure if significant peristaltic movement is encountered.
Special attention should be made to patients who are taking antiplatelet and anticoagulation agents. With the exception of aspirin, these medications should be stopped before the procedure to reduce the risk of intraoperative or postoperative hemorrhage.
A standard high-definition video gastroscope is used for most ESD procedures in the stomach. Today these scopes are equipped with an auxiliary water-jet channel; this helps clear the view during the dissection, especially when bleeding occurs. It is important that normal saline be used to fill the pump of the water-jet channel as water may reduce the conduction of electricity leading to ineffective electrosurgical dissection. The use of a transparent hood is recommended as it helps with stabilization of the scope position when carrying out submucosal dissection. Occasionally for ESD in difficult positions such as the fundus or lesser curvature of the antrum, the use of a multibending endoscope is necessary to allow access to the lesions for dissection.
Careful assessment of the lesion is imperative to ensure adequate resection margin and precise marking prior to mucosal incision. Early adenocarcinoma of the stomach usually has a well-defined demarcation line from adjacent normal mucosa and is visible with image-enhanced endoscopy. A gastroscope equipped with magnification and image-enhanced endoscopy technology such as Narrow Band Imaging (Olympus) or Blue Light Imaging (Fujifilm) can be used to evaluate the margin of the lesion and perform preprocedural marking. Additional dye-spraying chromoendoscopy with indigo carmine is also very helpful in determining the margin.
Endoscopic Submucosal Dissection Knives, Hemostatic Instruments, and Electrosurgical Unit
ESD requires the use of specially designed endoscopic knives for mucosal incision and submucosal dissection. Over the past decade numerous knives have been developed specifically for the procedure. These knives can be broadly categorized as “insulated” or “noninsulated” types. Recently, ESD knives with a water-jet channel have gained much popularity because these can decrease the need to exchange instruments during the procedure.
The ITKnife2 (Olympus) has an insulated ceramic tip that reduces the risk of perforation by avoiding deep muscular damage during submucosal dissection (Figure 20-1A). It is a popular device for gastric ESD. During mucosal incision, the direction of cutting should be from far to near of the view of the endoscope.
Noninsulated knifes, such as the DualKnife J (Olympus) (Figure 20-1B), FlushKnife BT (Fujifilm) (Figure 20-1C) enable dissection directly with the tip of the instruments. The procedure can be carried out precisely with direct visualization of the dissection plane. The risk of perforation is higher, however, if the tip is in contact with the muscularis propria layer. Nonetheless, in a difficult situation such as significant submucosal fibrosis, these instruments are particularly helpful to cut through the scarred tissue. When using a needle-type knife for mucosal incision, the direction of movement should be from near to far of the view of the endoscope.
Coagulation forceps, such as the Coagrasper (Olympus) are useful instruments to coagulate bleeding vessels in the submucosa during dissection. Recently, a newer version, the larger-size forceps Coagrasper G, is available that can control vessels of larger caliber, especially those located in the body of the stomach.
A reliable electrosurgical unit is crucial to providing a desirable electric current to achieve cutting and hemostasis during ESD. Our center uses the VIO300D (Erbe). The settings for gastric ESD are listed in Table 20-1.
Sodium hyaluronate (MucoUp, Johnson and Johnson) is the most common component used in the injection solution. Its viscous property, when added to normal saline, allows the fluid to stay within the submucosal space for a longer period of time. Adrenaline also is added to the mixture for its vasoconstrictive effect. Some endoscopists prefer to use a dye such as indigo carmine in the solution so the submucosal layer is blue for easier recognition. Glycerine solution has also been used as a substitute for sodium hyaluronate in countries where it is not readily available.
Planning of Endoscopic Submucosal Dissection
It is important to plan the ESD procedure to ensure a smooth resection. Generally, the steps of ESD include marking, submucosal injection, mucosal incision, submucosal dissection, and hemostasis. Conventional ESD begins with completion of the circumferential mucosal incision followed by submucosal dissection. The drawback of complete circumferential incision is that the specimen side of mucosa may shrink to a smaller size, loosening tension as well as the submucosal fluid cushion and making submucosal dissection more difficult. Alternatively, we could also commence with partial mucosal incision, proceed after with submucosal dissection beneath the incised area, and then complete the mucosal incision when a good submucosal dissection flap has been made. The “near-side” approach, reported by Mori et al, was found to significantly shorten the procedure time compared with the conventional approach.6 The efficacy of this technique was also demonstrated by the pocket creation method reported by Miura and colleagues.7
Generally, the scope position is more stable at a retroflex position, and submucosal dissection can easily be carried out by rotating the scope. This scope position is particularly favorable for lesions located at the lesser curvature and the proximal part of the stomach. In addition, the direction of gravity is an important consideration when planning submucosal dissection. Gravity serves to achieve a countertraction force to lift up the submucosal flap for easier identification of the dissection plane. The patient should be placed in the left lateral position so that the proximal stomach is more dependent than the distal part, thus dissection from distal to proximal with the aid of gravity would be advantageous.
Unlike in the colon, the margin of an early gastric cancer becomes indistinct after submucosal injection. As a result, preprocedural marking is crucial to ensure an adequate lateral resection margin. Each marking should be placed in appropriate proximity so the site of the next marking can be seen in the endoscopic view during mucosal incision. (Figure 20-2). Chromoendoscopy with indigo carmine is a useful adjunctive technique for margin assessment. Marking should be made 1 cm outside the lesion to allow an adequate margin. In situations for which chromoendoscopy fails to identify the exact margin, magnifying endoscopy with narrow-band imaging can be employed to locate the margin of the lesion more than 70% of the time.8 Defining margins of undifferentiated cancers is particularly difficult, and optical endoscopic assessment can underestimate the extent of the lesions because of subepithelial extension without mucosal features. In such situations some experts advise taking biopsies at the “normal mucosa” around the lesion to confirm the exact horizontal margins.
After marking the lesion, submucosal injection would be performed using a mixture of normal saline, adrenaline, and sodium hyaluronate. Mucosal incision with a needle type of ESD device starts from the near side toward the far side. When using the ITKnife2, a small incision should be made by a needle-type ESD device at the far side so the noninsulated part of the ITKnife2 can be placed into the submucosa for incision. During mucosal incision, the depth of the incision should pass beyond the muscularis mucosae to reach the submucosa.
As mentioned above, it is not necessary to complete the circumferential mucosal incision before submucosal dissection. The “near-side” approach entails mucosal incision of the “near side” for one-third to one-half of the circumference and submucosal dissection of the incised part, followed by complete mucosal incision and submucosal dissection of the remaining part.
During submucosal dissection of gastric lesions, the optimal layer for dissection should be at the deep submucosa just above the muscularis propria (Figure 20-3). At the submucosal layer, penetrating vessels branch off and give rise to multiple smaller vessels at the superficial part of submucosa, so one would encounter fewer vessels by dissecting deep in the submucosa. Moreover, the specimen obtained by dissecting deep submucosa contains a thicker submucosa, which could reduce the chance of vertical margin involvement for gastric cancer with submucosal invasion.
Large penetrating submucosal vessels should be coagulated using a Coagrasper prophylactically before cutting. These vessels are seen more frequently at the lesser curvature of the stomach, where the inner oblique muscles can also be identified. The submucosal layer is more fibrous in this area, which increases the difficulty of performing ESD for tumors in the proximal lesser curvature. Hence the submucosal dissection should be performed in a more cautious manner in this area.
After en bloc resection of the tumor, the specimen should be retrieved with either endoscopic forceps or a Roth Net retriever. Meticulous hemostasis of the ESD artificial ulcer base is important to prevent secondary hemorrhage. The usual technique of hemostasis after ESD includes identifying a visible vessel, grasping the vessel with a Coagrasper, and achieving complete sealing of the vessel using soft coagulation mode. Previous study has suggested that prophylactic coagulation of visible vessels could reduce the risk of delayed bleeding.9