Ultrasound endoscopy = ultrasound + endoscopy Ultrasound endoscopy is an intracavitary ultrasound technique mediated by endoscopy. There are 2 methods of ultrasound endoscopy: 1. A miniature high-frequency ultrasound probe is installed at the front end of the endoscope; 2. A miniature ultrasound probe is inserted through the biopsy clamp tract during endoscopy. The high frequency is selected to observe the lesion in close proximity. Ultrasound endoscopy not only can play the role of ordinary endoscopy, but also can clearly display the tomographic images of submucosal lesions and their adjacent organs on the screen. Chronic gastritis, peptic ulcer and other diseases can be completely diagnosed clearly with ordinary gastroscopy with pathological examination; benign polyps and augmented erosive gastritis diagnosed under ordinary endoscopy do not need to be examined by ultrasonic endoscopy, and pathological examination is required. Ultrasound endoscopy is mainly used for endoscopy or barium contrast examination of the digestive tract to discover the lesion, and further understanding of the level of the gastric wall where the lesion is located, the depth of lesion invasion, and the organs or lymph nodes outside the gastric cavity is needed. This examination is usually recommended for submucosal augmentation lesions. Ultrasound endoscopy is also used for the differential diagnosis of submucosal tumors of the gastrointestinal tract, the staging of the course of gastroesophageal cancer (depth of tumor infiltration, presence of metastases in surrounding lymph nodes and adjacent organs), the diagnosis of pancreatic tumors, stones in the lower end of the common bile duct, and other diseases, especially the staging of malignant tumors of the gastrointestinal tract, which is very important in deciding the surgical approach and prognosis. Under the guidance of ultrasound endoscopy, puncture biopsy and interventional treatment can also be done. Because of the high sensitivity and safety of ultrasound endoscopy for the diagnosis of submucosal tumors of the gastrointestinal tract, gastric cancer staging and pancreatic diseases, it has been popularly used in many hospitals in China.