Endoscopic Ultrasonography (EUS) is an interventional ultrasound diagnostic technique that involves placing an ultrasound probe at the tip of the endoscope, which allows direct observation of the luminal morphology of the gastrointestinal tract through the endoscope while allowing real-time ultrasound scanning to obtain histological structural features of the canal wall level and ultrasound images of the surrounding adjacent organs, thus further improving This further improves the diagnostic level of endoscopy and ultrasound. The ultrasound probe is close to the lesion site – No abdominal wall attenuation and gastrointestinal gas influence – High ultrasound frequency and clear image The advantages of ultrasound endoscopy compared with ordinary endoscopy: – The depth of the lesion can be understood – Diagnosis and differential diagnosis of submucosal masses in the gastrointestinal tract – Diagnosis and preoperative TNM staging of malignant tumors in the digestive tract – Peripheral masses in the gastrointestinal tract Qualitative – Diagnosis and differential diagnosis of pancreaticobiliary diseases – Intra-ductal ultrasound (IDUS) combined with ERCP – Ultrasound endoscopy-guided aspiration (FNA), duct placement, cholangiography, abdominal ganglion block (CPN), internal drainage of pancreatic pseudocysts IV. Classification of EUS – According to the scanning mode, it is divided into line array ultrasound endoscopy and circular scanning ultrasound endoscopy. – According to the probe movement mode, it is divided into electronic trigger type and mechanical rotation type. – According to the structure of the instrument, it is divided into fiber ultrasound endoscope, electronic ultrasound endoscope, Doppler ultrasound endoscope, three-dimensional ultrasound endoscope, ultrasound small probe, etc. – According to the examination site, it is divided into ultrasound gastroscopy, ultrasound enteroscopy, ultrasound laparoscopy, etc. V. Indications for EUS – Diagnosis of suspicious cancerous lesions in the digestive tract and determination of the depth of infiltration; – Diagnosis of submucosal tumors: such as smooth muscle tumors, mesenchymal tumors, lipomas, etc.; – TN staging of malignant tumors in the digestive tract; – Peptic ulcers; – Pancreatic lesions, such as chronic pancreatitis, pancreatic tumors; – Biliary system diseases, such as common bile duct stones, biliary tract tumors; – Determining the degree of esophageal varices and the efficacy of embolization therapy; – Can show some mediastinal lesions. Contraindications to EUS (1) Absolute contraindications: ① Severe cardiopulmonary disorders that cannot tolerate endoscopy. (2) Those in critical condition such as shock. (3) Those who are suspected of having gastric perforation. ④ Uncooperative psychiatric patients or those with severe mental retardation. ⑤ Acute inflammation of the oral cavity, pharynx, esophagus and stomach, especially corrosive inflammation. ⑥ Others: obvious thoracic aortic aneurysm, cerebrovascular accident, etc. (2) Relative contraindications: ① Giant esophageal diverticulum, obvious esophageal varices or high-grade esophageal cancer, high spinal deformity. (2) Those with cardiac and other important organ insufficiency. ③ Those who have uncontrolled hypertension. 7. Complications of EUS 1. Asphyxia: The incidence is very low, mainly due to changing the patient’s position during ultrasonic endoscopy with excessive water injection in the stomach. 2, aspiration pneumonia: less frequent, often due to inadvertent aspiration of gastric fluid or excessive water injection during the procedure. 3, device injury: there are pharyngeal injury, esophageal perforation, gastric perforation, intestinal perforation, gastrointestinal wall abrasions, etc. As ultrasonic endoscopy is coarser than gastroscopy, patient discomfort is more obvious than gastroscopy, and pharyngeal injury is more common. 4, Bleeding. 5.Anesthesia accident. Pre-operative preparation and post-operative precautions- Pre-operative preparation: Same as gastroscopy: fasting for 6-8 hours before surgery, fasting after 8:00 p.m. the day before for morning examinations, and eating a dregs-free semi-liquid diet in the morning of the same day for afternoon examinations, and fasting at noon. Pre-operative oral lidocaine syrup. – Post-operative precautions: Usually only fasting and abstaining from food and drink for 2 hours after surgery is required.