Colorectal ESD using DualKnife J

Endoscopic submucosal dissection (ESD) was initially developed for gastric lesions in the late 1990s and was subsequently adapted for colorectal lesions. More than a quarter of a century has passed since the technique was first developed. Over this time, exciting new devices have been developed and methodologies have also evolved. Ideally, each physician should use the procedures and devices that suit them best. Needle-type knives are used universally in current colorectal ESD in Japan. This article discusses strategies for colorectal ESD in actual cases using needle-type knives.

Before presenting cases, I will discuss the incision device I use. As for “Which knife is best?”, the optimal answer is to select the one that best aligns with your preferences, based on an understanding of the characteristics of each knife. Because the muscularis propria is thin, colorectal ESD requires precise incision and dissection. Needle-type knives are very useful from this standpoint.
The DualKnife J has a knob-shaped tip. With a tip diameter of 0.65 mm and a knife diameter of 0.4 mm, it can hook incised tissue without slipping and allows steady insertion of the knife tip even into narrow gaps, thanks to its moderate diameter. In addition, it has a jet function which allows dissection while delivering fluid to the submucosal layer.

Let’s begin with a relatively basic case (Fig. 2a).

Introduction into the submucosal layer is widely regarded as difficult in colorectal ESD. What physicians mean by this is that it can be hard to penetrate the endoscope into the submucosal layer. In this regard, the initial local injection is crucial. If the local injection reliably elevates the lesion and causes the proximal part of the lesion to swell like a bun, then the first incision can open up the optimal layer immediately. When performing the initial local injection, focus on creating the “shape” of that injection yourself.
Fig. 2 shows the initial phases of case 1, illustrating how a properly executed local injection allows wide spreading with a single incision and facilitates subsequent introduction into the submucosal layer.

The importance of proper local injection is as described above, but proper “introduction into the submucosal layer”, i.e., entry of the scope tip beneath the mucosal flap, also leads to a favorable result, after which you simply proceed with dissection (Fig. 3). Merely incising the mucosa does not allow introduction into the submucosal layer, even if you try to insert the hood by force. Introduction into the submucosal layer may be possible after removing submucosal tissue a few times in the optimal manner, but this means that you must hold the proximal mucosa so that a large portion of the submucosal layer which you are going to cut is exposed, as shown in Fig. 4. In this figure, the mucosa is carefully held with the DualKnife J’s knob-shaped tip. A similar effect can be obtained by properly using the 6 o’clock position of the distal hood. Even so, it is still not easy to penetrate the layer with a single sweep.
Among the techniques that would facilitate introduction into the submucosal layer, one that can be used with DualKnife J is to “lift up with the tip”, as shown in Fig. 5. Lift the lesion flap with the sheath of DualKnife J and, after visually recognizing the submucosal layer you are going to cut, adjust the position as if aligning the knob-shaped tip with that line. The key here is to achieve maximum deaeration (introduction into the submucosal layer is impossible if the lumen is completely filled with insufflated air) and to gently lift the layer with the tip of the hood (Fig. 6).

The first thing to do after introducing the DualKnife J into the submucosal layer is to excavate the blue submucosal layer in front of you toward the most distal position possible. Rather than immediately proceeding to circumferential incision, dig and advance in the central part immediately beneath the lesion. This is known as the pocket-creation method (PCM)¹. After widening the pocket to a certain extent, perform dissection with the goal of opening the pocket to both the left and right (Fig. 7).
What is important here is to advance dissection by making use of the DualKnife J’s precision. Your goal should be to remove fibers one by one along the optimal dissection line.

When fibrosis is present, introduction into the submucosal layer becomes even more difficult. This case has a higher degree of difficulty than Case 1. It is a IIc lesion near an anastomotic site of the descending colon after surgery, accompanied by severe cramping and depression (Fig. 8).

In cases with fibrosis, the knife’s jet function is particularly useful. Fig. 10 shows a mid-procedure phase in which the fibrotic region has been exposed by digging on both sides. Because secure preservation of the dissection space is desirable at this stage, the usual approach is to switch devices and insert a local injection needle. However, changing devices takes time, and it is not uncommon for the field of view to change during that interval. Instead, using the DualKnife J’s jet function allows you to proceed rapidly with dissection while delivering fluid.
When local injection is performed with a needle, the submucosal cushion may dissipate when the device is　switched to the knife. The jet function, on the other hand, makes it possible to start dissection at the exact moment the submucosal layer is elevated.
The procedure to use the jet function is simple: 1) Retract the tip; 2) Lightly touch the target area with the sheath tip to deliver the liquid press the coagulation wave pedal on the electrosurgical unit; 3) Project the knife tip; 4) Start the jet function through the knife.
This enables effective elevation of the submucosal layer. Efficient delivery is also possible by connecting a water-jet pump to the knife. If delivering saline, you can attach a 5–10 cc syringe externally to the knife and push by hand (Fig. 11).
In this case, it would also be acceptable to use a traction device at the initial stage. We will show an example using traction in another case: an LST that appears to enter the ileocecal valve. Although the terminal ileum side of the lesion is difficult to see, applying traction after incision makes it easier to identify the resection line. Applying a second traction device in a different direction can further facilitate resection (Fig. 12).