Novel electrosurgical knife with adjustable sheath length for colorectal endoscopic submucosal dissection

During endoscopic submucosal dissection (ESD), it is important to resect the submucosal layer under endoscopic view and confirm the absence of muscular layer damage.1-4 However, during colorectal ESD, it is difficult to control the endoscope while simultaneously controlling the tip of the electrosurgical knife with the right hand. Video S1 demonstrates a newly designed electrosurgical knife (TechKnife T-type; Micro-Tech, Nanjing, China) that allows assistants to shorten the knife's sheath; this helps maintain endoscope visibility. This knife allows local injection from the tip of its needle. When the assistant opens the knife's handle, the needle emerges from the sheath's tip (Fig. 1). The knife is stored in the tip when the handle is closed; when closed firmly, the entire sheath is retracted towards the accessory channel by ˜1 cm. These features allow an endoscopic view of the submucosal dissection. Our patient developed recurrent, early colorectal cancer following a piecemeal endoscopic mucosal resection. The lesion was completely resected through saline-immersion ESD using a 4-mm, calibrated, small-caliber-tip, transparent hood (CAST hood), because fibrosis was expected to be under the lesion.5 The assistant closed the knife handle firmly to check for inadvertent damage to the muscularis propria, and the knife was retracted into the accessory channel (Fig. 2). This allowed the main operator to maintain an appropriate submucosal endoscopic view while holding the endoscope in his right hand. The lesions were resected en bloc with negative margins.

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(a) Needle emerges from the knife tip (knife handle is opened). (b) Needle is inside the knife tip (knife handle closed weakly). (c) Knife tip is retracted and the sheath is shortened (knife handle is closed firmly).

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(a) Submucosal dissection with the knife needle out (knife handle is open: red circle). (b) The submucosal layer is visible because the knife sheath has been shortened, and the needle is retracted (knife handle is closed firmly: red circle).

In conclusion, during intestinal ESD, sheath-length adjustment in the new knife ensured safe dissection while the endoscope was held in the right hand. This knife is useful for not only rectal ESD, but also for other gastrointestinal ESDs, especially where endoscopists lack complete control over the scope if their right hand is not holding it. However, assistants require some experience prior to using this knife.

Authors declare no conflict of interest for this article.

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