Endoscopic submucosal dissection, a promising technique for clinical application, allows more early gastrointestinal cancers to be completely removed in one go under endoscopy, eliminating the pain of open surgery and organ removal. ESD mainly treats the following GI lesions: 1.Early stage cancer and precancerous lesions: According to the pathological results, combined with other endoscopic examination methods such as staining, magnification and ultrasound, it is determined that the tumor is confined to the mucosal layer and the submucosal layer without lymphatic metastasis, and the resection of tumor by ESD method can achieve the same therapeutic effect as surgery. 2.Large flat polyps: for polyps over 2 cm, especially flat polyps, ESD treatment is recommended to remove the lesion once and completely. 3.Submucosal tumors: lipomas, mesenchymal tumors, ectopic pancreatic and carcinoid tumors diagnosed by ultrasound endoscopy can be completely peeled off the lesion by ESD if the location is shallow (from the myxomucosal and submucosal layers). Preoperative preparation All patients were admitted to the hospital for treatment, and routine blood, biochemical and blood group tests were performed to determine normal coagulation profile before ESD was performed. For patients with lesions in the upper gastrointestinal tract, painless anesthesia was routinely performed. For patients with lesions in the rectum or sigmoid colon, the procedure can be performed while they are awake. Instruments used GI endoscope, high-frequency electric generator, needle scalpel, end-insulated scalpel (IT knife), hooked electric knife, trap, thermal biopsy forceps, argon gas knife, metal titanium clips, water injection pump, etc. The needle-type incision knife is used to cut through the mucosal layer and submucosal layer. IT knife is a small ball with insulating magnetic material at the head end to reduce the vertical distance of energization and reduce the risk of perforation when cutting perpendicular to the wall of the digestive tract. Hooked electric knife is used for separation and cutting of connective tissue between the submucosa and the muscular layer. Surgical method After endoscopic examination to determine the location of the lesion, staining is first performed. If the lesion is located in the esophagus, iodine staining is performed; if it is located in the stomach or rectum, US blue or 0.1% to 0.4% indigo carmine staining is performed. Microprobe ultrasound endoscopy was applied to determine whether the lesion was located in the mucosal or submucosal layer. When the lesion was located in the mucosal layer, glycerol fructose solution containing melanin was injected into the submucosa of the lesion, and a needle incision knife was used to mark the border and extent of resection. The needle knife is used to make the opening, and the IT knife is used to make the incision and peel. If bleeding occurs during the operation, the bleeding is stopped by electrocoagulation with the IT knife, TT knife or hot biopsy forceps; if bleeding does not stop, a hemostatic clip can be used to stop the bleeding. Peel the lesion as completely as possible, and if peeling is difficult, use a trap to assist in electrodesiccation. After surgery, fix the specimen and send it directly to the pathology department for pathological examination. Complications: The most significant complications of ESD are bleeding and perforation. In the event of intraoperative bleeding or discovery of vascular exposure, direct hemostasis can be achieved with an electric knife, hot biopsy forceps, and metal titanium clips. Postoperatively, all residual vessels seen in and around the mucosal trauma are completely eradicated to prevent delayed bleeding. During the operation, if signs of perforation are found or if there is a risk of such a perforation, titanium metal clamps can be used to close the wounds at risk of perforation to prevent perforation for therapeutic purposes. Close postoperative observation: After the operation, the patient is given routine fasting, water, bed rest, and observation for 24 to 48 hours. Proton pump inhibitors, hemostatic agents, antibiotics, etc. are used. If there is no vomiting of blood, black stool, abdominal pain, or subcutaneous emphysema, the patient may be placed on a liquid diet on the third postoperative day. If abnormalities occur during this procedure, the fasting time should be extended and a gastric tube may be placed for gastrointestinal decompression if necessary. The ulcers formed by ESD surgery are easier to heal than pathological ulcers, and generally recover completely in 1 to 2 months after surgery.