The contact area is one of the most important factors determining the characteristics of the specific knife. A knife with a smaller contact area usually produces a rapid and effective cut due to a higher current density with limited coagulation effect. The standard needle knife and an insulation-tipped (IT) electrosurgical knife (IT knife and IT-2 knife; KD-610 L and KD-611 L; Olympus Co., Tokyo, Japan) are mainly used for performing gastric ESDs. Since the colorectal wall is thinner than the gastric wall and the submucosal space is narrower, but with less vasculature, knives for colorectal ESD should have a short blade length and, ideally, some safety feature to prevent muscularis propria injury. The conventional resection knives and the resection knives with integrated fluid injection capability used during ESD and currently available in the West are summarized in Table 3 [26−32].

Submucosal injection solutions are used to lift lesions, separating mucosa from muscularis propria, but the lengthier ESD procedure (as compared to endoscopic mucosal resection (EMR)) requires prolonged elevation of the mucosa to expose the submucosal layer to facilitate submucosal dissection. Thus, the agent used for ESD must be long-lasting, safe, easy to handle, and easy to inject. In order to meet these criteria, many injection agents have been thoroughly evaluated, with some becoming commonly used. Sodium hyaluronate is now commercially available in Japan as a dedicated injection agent for ESD (MucoUp®, Johnson and Johnson Medical Co., Tokyo, Japan).

Hypertonic saline solution and dextrose are inexpensive and readily available, but both can cause tissue damage [33]. On the other hand, fibrinogen is a good submucosal cushion [34]; but, since this agent is derived from human serum, it has been criticized as a potential vehicle for viral transmission. Sodium carboxymethylcellulose [35], endoscopic lubricant jelly (Null Jelly) [36], and photocrosslinkable chitosan hydrogel may be other choices [37], but further study is necessary to verify the safety and efficacy of these alternatives. One of the most commonly used agents in Japan is Glyceol (Chugai Pharmaceutical, Tokyo), which consists of 10 % glycerol and 5 % fructose in normal saline, combined with a small amount of sodium hyaluronate [38].

Diluted epinephrine (1:100,000 to 200,000) mixed into the submucosal injection agent has been reported to reduce immediate bleeding during the endoscopic procedure [39]. However, due to the limited clinical evidence, its use is variable and may not be necessary for colorectal ESD. Indigo carmine may also be added to the injection solution to help in visualizing the area to dissect (utilizing minimum amount necessary for adequate coloring). Finally, lidocaine (1 %) has been used as a local anesthesia for rectal ESD close to the dentate line, though this may not be necessary [40].

A transparent distal attachment (hood or cap) can be mounted on the tip of the endoscope to assist the safe and controlled use of an ESD knife. The hood pushes the resected mucosa or surrounding tissue away from the cutting plane, thus, creating countertraction and allowing better and clearer visualization of the working area. It is also useful for temporary hemostasis by tamponading the bleeding point with the tip of the hood to stop bleeding while the ESD knife is exchanged for hemostatic forceps.

The small-caliber-tip transparent (ST) hood (DH-16GR or DH-16CR; Fujifilm, Tokyo, Japan) has a tapered aperture and enables the operator to easily open up the incision to dive into the submucosal layer and accurately adjust the depth of incision that is made with the tip of the knife. Short ST hoods with a 1 mm larger opening tip than conventional ST hoods (8 mm versus 7 mm) have been developed (DH-28GR, DH-29CR, or DH-30CR; Fujifilm, Tokyo, Japan), but are not yet available in the USA [41].

Various other types of attachments can be chosen depending on the needs or situation (e.g., an attachment with holes to drain water or blood) [42]. The KUME hood (Create Medic, Yokohama, Japan) is a soft transparent distal attachment with a thin tube. It provides a jet of water via the tube attached to a water-filled syringe. Impact Shooter (Top Co., Tokyo, Japan) enables the endoscope to work like a dual-channel scope. Air Assist (Top Co., Tokyo, Japan) is a soft balloon that fits outside the endoscope, proximal to the bending area of the endoscope. It enables the endoscope to mimic a multibending scope. The EndoLifter (Olympus, Tokyo, Japan) is a distal attachment with grasping forceps that can be used to grasp the mucosa. Once the proximal area is cut and the mucosa grasped with the EndoLifter, the submucosal layer is revealed, creating easier access to the dissection plane of the submucosa; however, the proposed benefit is not consistently provided [42].

A high-performance ESU is indispensable for every step of the ESD procedure: marking, precutting, circumferential cutting, submucosal dissection, and hemostasis. Older ESUs only had one power setting, but the VIO series ESUs (VIO 200D, VIO 300D, ICC350, ERBE Elektromedizin, Tuebingen, Germany) have a sensor that can control the power automatically and adjust to the circumstance [20]. Each unit detects and monitors the current, power, and spark that create the cutting by controlling voltage. Therefore, the procedure can be performed in a smooth and steady manner.

There are various kinds of electric modes, each of which is used for a different purpose. The indications and characteristics of each type of current are summarized in Table 4.