The detection rate of superficial gastrointestinal neoplasms, including precancerous lesions and early cancer, increases with the popularity of endoscopic examination and development of endoscopic technique. Meantime, endoscopic submucosal dissection (ESD) has been recognized as one standard and minimally-invasive treatment for en bloc resection of gastrointestinal neoplasms [1, 2]. However,two problems would occur fro the dissection of large lesions using the standard procedure ESD, one of which is that the lifting effects of submucosal injection is quite different before and after circumferential incision and more specifically is less obvious after circumferential incision, the other of which is that when the dissection reaches the central part of a large lesion, the endoscopic vision is obscured because the space for maneuvering the endoscope becomes confined mainly due to the contraction of the dissected part of the lesion [3, 4]. These problems make further dissection difficult, unsafe and time-consuming. To overcome these difficulties, modified fishing-line traction system (Fig. 6.1) and “medical ring” (Fig. 6.2) have been devised in ESD procedure for resection of large esophageal tumors and early gastric cancer respectively [5, 6]. In the procedure of resecting large lesions, these methods can avoid the obstruction of endoscopic view from resected mucosa, but they cannot be applied easily or conveniently.

The tunnel technique develops rapidly, and promising results have been shown in clinical studies and animal experiments [7–16]. In this technique, one submucosal tunnel is created to provide working space for further endoscopic interventions, such as cutting the muscularis propria in the treatment of achalasia, removing gastrointestinal submucosal tumors, or even allowing access to the peritoneal and thoracic cavity for further interventions. Since 2009, Professor Enqiang Linghu has attempted to improve ESD procedure by use of tunnel technique [7, 8], namely endoscopic submucosal tunnel dissection (ESTD). In ESTD procedure, one submucosal tunnel extending from oral margin to anal margin is established to facilitate en bloc resection of the lesions. ESTD has been applied in esophageal circumferential lesions, large esophageal lesions and gastric large lesions, and proved to be safe and effective [3, 4, 8, 9].

The procedure of the standard ESD includes marking, injection, circumferential incision and dissection, while the procedure of ESTD is different and includes marking, injection, anal incision, oral incision, tunnel establishment and bilateral resection [3, 4].

During ESTD procedure, the anal incision is made before the tunnel creation. The anal incision can serve as the endpoint of the tunnel so that the submucosa will not be dissected immoderately. In addition, the anal incision can prevent abundant gas from over accumulation during the creation of the tunnel, which might result in extra mucosal separation [3, 4].

The following points may explain the advantages of ESTD [3, 4]: (i) The transparent cap attached to the endoscope has an effect of blunt dissection with the moving forward of the endoscope; (ii) The use of CO₂ as the insufflation gas during ESTD also has an effect of blunt dissection and could work as a gas cushion since the CO₂ increases the distance between the mucosa and the muscularis propria. (iii) Since the dissection is conducted during a tunnel, the submucosally injected solutions are well maintained in the submucosal layer and thus minimizing the amount of injection solutions and increasing the efficiency and safety of dissection. (iv) During submucosal dissection in the tunnel, the traction of the two sides of the tunnel avoids the effects of contraction and obstruction of resected mucosa, and contributes to keeping clear operative view and dissecting the submucosal layer. (v) In the procedure, blood vessels expose well and can be preventive coagulation, which reduces the incidence of bleeding and the time of hemostasis. Therefore, the operative view is clear and the speed of the operation improves accordingly.

The ESTD procedure in different locations described as following.