Endoscopic submucosal dissection (ESD) is a novel endoscopic resection technique that enables reliable en bloc resection of large and difficult gastrointestinal lesions. We initially performed ESD using the tip of a thin-type snare to serve as a blunt-end short needle knife. However, the device had limitations; therefore, we developed a more reliable and durable device, the Flex knife. It cut well in any direction and was easy to control because of its soft and flexible nature, making it extremely useful for ESD of colorectal and esophageal lesions that required delicate maneuvering. Although the Flex knife achieved excellent treatment results, its use was still technically limited by the loop-shape tip, resulting in difficulty with knife length adjustments, frequent intraprocedure accumulation of debris on the tip, and slippage of the knife tip away from the operating field. Therefore, we designed an improved version of the Flex knife, the Dual knife. It resembles a short needle knife with a small apical disk. It has a fixed knife length: 1.5 mm for esophageal and colorectal ESD and 2 mm for gastric ESD. The small disk is useful for marking and hemostasis in a closed position and for stabilization of the knife movement against scarred or floppy tissue in an opened position, resulting in overall improved knife maneuverability and durability. In the practical Flex and Dual knife technique, sufficient submucosal injection and partial incision as well as partial submucosal dissection is key for successful ESD. Combining the endoscopist's knowledge and skill with the soft and flexible properties of the Flex and the Dual knives results in relatively safe and highly effective ESD outcomes.
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