Endoscopic retrograde cholangiopancreatography (ERCP) is the most technically demanding and risky gastrointestinal endoscopic operation, which is the crown jewel of endoscopy. ERCP is a technique of retrograde cholangiopancreatography by injecting contrast agent through the duodenal papilla under the endoscope, which is currently recognized as the gold standard for the diagnosis of pancreaticobiliary duct disease, and has the advantages of no incision, less trauma, shorter operation time and shorter hospital stay, which will greatly facilitate patients’ medical treatment. While confirming the diagnosis, doctors can complete complex surgeries such as removing gallstones, placing stents, cutting tumors and unblocking bile ducts without opening the abdomen and using only a few millimeters thick endoscope, replacing to some extent the traditional surgical procedures for some digestive system diseases. ”Doctors who can skillfully perform ERCP must not only have the perception and skills of a surgeon, but also the delicacy and brains of an internist.” Li Zhaoshen, director of the Chinese Medical Association’s Division of Gastrointestinal Endoscopy, introduced ERCP as the most difficult technique to operate in gastrointestinal endoscopy, and there are only a thousand doctors who can skillfully apply ERCP clinically in China. Indications (1) Bile duct stones: After removing bile duct stones by duodenal endoscopy, it can replace traditional dissection bile duct extraction and T-tube drainage, without opening the abdomen and with little trauma. (2) Residual bile duct stones after cholecystectomy: stones can be removed endoscopically to avoid the pain of reoperation. (3) Acute biliary-derived severe pancreatitis: endoscopic nasobiliary drainage in 1-3 days in the early stage can improve the success rate of treatment. (4) Septic cholangitis: high mortality rate and high risk of traditional surgery, timely endoscopic biliary drainage for decompression can rapidly stabilize the patient’s condition and gain valuable time for surgical treatment. (5) Duodenal papillary cancer: early diagnosis is difficult, ERCP is clear at a glance and biopsy is possible. (6) Chronic pancreatitis and pancreatic duct stones. (7) Obstructive jaundice caused by bile duct cancer or pancreatic head cancer: stenting is feasible to resolve jaundice, delay liver failure and greatly prolong survival. Common complications Since ERCP is an invasive and minimally invasive technique, it inevitably brings certain complications, and even serious complications can be life-threatening. Although the incidence of ERCP-related duodenal perforation is low, the morbidity and mortality rate is high, especially in the vicinity of the duodenal papilla, which has a very high mortality rate. Both doctors and patients must be fully aware of the indications before surgery. The main diagnostic bases of perforation are: peritonitis and subcutaneous emphysema. Some minor perforations that can be detected early can be treated conservatively under endoscopy: endoscopic placement of internal drainage tubes and/or nasobiliary drainage, clamping of the perforation with titanium clamps, fasting with intravenous nutrition and antibiotics, and surgery in severe cases. Hemorrhage ERCP lithotomy requires incision of the duodenal papilla, and this operation often causes bleeding. Injurious bleeding can also occur from pancreaticobiliary duct dilatation and stent placement. In general, hemorrhage can be stopped endoscopically. For active hemorrhage that cannot be controlled by endoscopy, surgical intervention should be performed promptly to stop the bleeding. Infection ERCP surgery has a small invasive surface, and the incision is mucosal, which is highly resistant to infection, so local infection caused by ERCP incision is rare. However, after ERCP placement of biliary stents to treat biliary obstruction, stent occlusion can lead to biliary tract infection. In addition, contrast agents can also introduce bacteria and cause pancreaticobiliary tract infection. In case of infection, prophylactic antibiotics should be administered postoperatively. If the pancreaticobiliary duct infection is severe, timely drainage, reoperation with ERCP or surgical removal of the stent are required, but the risk of surgery is increased. Other complications include intestinal obstruction, antibiotic-associated diarrhea, liver abscess formation, pneumothorax/mediastinal pneumothorax, perforated colonic diverticulum, duodenal hematoma, and portal vein thrombosis.