Acute pancreatitis (AP) is a disease characterized by activation of pancreatic enzymes due to multiple etiologies, followed by a local inflammatory response of the pancreas with or without functional changes in other organs. Clinically, the course of the disease is self-limiting in most patients, and 20%-30% of patients have an aggressive clinical course. The overall morbidity and mortality rate is 5-10%. I. Terminology and definitions According to the AP grading and classification system developed by the International AP Symposium (Atlanta, USA, 1992) and the AP management guidelines issued by the World Congress of Gastroenterology (Bangkok, Thailand, 2002), and taking into account the specific situation in China, the terminology and definitions of AP are stipulated with the aim of guiding clinical and scientific work and regulating academic terminology in this field. (A) clinical use of terms 1, AP: clinically manifested as acute, persistent abdominal pain (occasionally without abdominal pain), increased serum amylase activity ≥ 3 times the upper limit of normal value, imaging suggests pancreatic with or without morphological changes, excluding other diseases. Other organ dysfunction may or may not be present. In a few cases, serum amylase activity is normal or mildly increased. 2, Mild AP (MAP): with clinical manifestations and biochemical changes of AP without organ dysfunction or local complications, and responding well to fluid supplementation therapy. Ranson score of 38.5°C, WBC>16.0)38.5°C, WBC>12.0)150 mg/L suggests pancreatic tissue necrosis. Increased serum interleukin-6 level measured dynamically suggests poor prognosis. 3. Imaging diagnosis: Ultrasound examination performed at the initial 24-48h of onset can initially determine the morphological changes of pancreatic tissues and also help to determine the presence of biliary tract diseases, but the influence of gas accumulation in the gastrointestinal tract during AP cannot make accurate judgment on AP. CT scan is recommended as the standard imaging method to diagnose AP. Enhanced CT or dynamic enhanced CT examination is performed if necessary. Grade A: normal pancreas according to the severity of inflammation. grade B: pancreatic parenchymal changes, including local or diffuse glandular enlargement. grade c: inflammatory changes in and around the pancreatic parenchyma with mild peripancreatic exudation. grade D: significant peripancreatic exudation in addition to grade c, with a single fluid accumulation in or around the pancreatic parenchyma. grade E: extensive intra- and extra-pancreatic fluid accumulation, including pancreatic and fat necrosis, and pancreatic abscess. grade A Grade -c: clinically MAP; Grade D-E: clinically SAP. 4. Recommendations: (1) The importance of clinical manifestations in the diagnosis of AP must be emphasized. Persistent mid-upper abdominal pain, increased serum amylase, and imaging changes, excluding other diseases, can diagnose this disease. (2) The clinical term “moderate AP” or “severe AP tendency” is no longer applied. (3) Clinical attention should be paid to the possibility of conversion of some AP patients from MAP to SAP. Therefore, dynamic observation of the disease is necessary. In addition to Ranson index and APACHE-II index, other valuable discriminatory indicators are: body mass index over 28kg/m2; pleural exudate, especially bilateral pleural effusion: CRP>150mg/L after 72h, and continues to increase, etc. are all valuable clinical indicators for severity assessment. Second, the principles of AP management 1, the initial treatment and monitoring: the purpose is to correct water and electrolyte disorders, supportive treatment, and prevent local and systemic complications. Contents include: routine blood and urine measurement, fecal occult blood, kidney function, liver function measurement; blood glucose measurement; cardiac monitoring; blood pressure monitoring; blood gas analysis; serum electrolyte measurement; chest X-ray; central venous pressure measurement. Dynamic observation of abdominal signs and bowel sound changes. The 24-h urine output and volume changes were recorded. The above indicators can be selected according to the patient’s specific condition. Routine fasting Gastrointestinal decompression should be performed for those with severe abdominal distension and paralytic intestinal obstruction. Open diet can be considered when abdominal pain is reduced or disappeared, abdominal distension is reduced or disappeared, and intestinal dynamics is restored or partially restored, starting with sugar-based diet and gradually transitioning to low-fat diet, without taking high or low serum amylase activity as a necessary condition for open diet. 2. Fluid rehydration: The amount of fluid rehydration includes the amount of basic needs and the amount of fluid flowing into the tissue interstitial space. Attention should be paid to infusion of colloidal substances and supplementation of trace elements and vitamins. 3.Analgesia: Consider analgesic treatment when the pain is severe. Pethidine hydrochloride (Dulcolax) can be injected under close observation of the condition. It is not recommended to apply morphine or cholinergic receptor antagonists, such as atropine, 654-2, etc., because the former will contract the sphincter of Oddi, and the latter will induce or aggravate intestinal paralysis. 4, inhibition of pancreatic exocrine secretion and pancreatic enzyme inhibitor application: growth inhibitor and its analogues (octreotide) can play a role by directly inhibiting pancreatic exocrine secretion, which is advocated for application in SAP treatment. H2 receptor antagonists and proton pump inhibitors can indirectly inhibit pancreatic secretion by inhibiting gastric acid secretion, in addition to preventing the occurrence of stress ulcers, which is advocated for use in SAP. Protease inhibitors are advocated to be applied early and in sufficient quantity. Application of vasoactive substances: Since microcirculatory disorders play an important role in the pathogenesis of AP, especially SAP, it is recommended to apply drugs that improve microcirculation in the pancreas and other organs, such as prostaglandin E1 preparations, platelet-activating factor antagonists, salvia preparations, etc. 6, antibiotic application: for non-biliary MAP is not recommended for the routine use of antibiotics. For biliary MAP, or SAP, antibiotics should be used routinely. The causative agents of pancreatic infection are mainly gram-negative bacteria and anaerobic bacteria and other intestinal resident bacteria. The application of antibiotics should follow three major principles: antibacterial spectrum for gram-negative and anaerobic bacteria mainly, strong lipid solubility, and effective passage through the blood-pancreatic barrier. Metronidazole combined with quinolones is recommended as the first-line drug, and in case of poor efficacy, other broad-spectrum antibiotics should be used instead, with a course of 7-14 d. The application can be extended in special cases. It is important to pay attention to the diagnosis of fungal infection. When fever and other manifestations cannot be clinically explained by bacterial infection, the possibility of fungal infection should be considered, and antifungal drugs can be applied empirically, and fungal cultures of blood or body fluids can be performed at the same time. 7.Nutritional support: MAP patients only need short-term fasting, so they do not need enteral or parenteral nutrition; SAP patients often implement parenteral nutrition first, and then consider implementing enteral nutrition when the condition tends to be in remission. The implementation of enteral nutrition means placing the nasal feeding tube distal to the Treitz ligament and infusing the elemental nutrients with an energy density of 4.187 J/ml. If the energy is insufficient, parenteral nutrition can be supplemented and the patient’s response can be observed, and if tolerated, the dose can be gradually increased. Attention should be paid to supplementation with glutamine preparations. For patients with hyperlipidemia, the supplementation of fatty substances should be reduced. When performing enteral nutrition, attention should be paid to whether the patient’s abdominal pain, intestinal paralysis, abdominal pressure and other symptoms and signs of pancreatitis are aggravated, and electrolytes, blood lipids, blood sugar, total bilirubin, serum albumin level, blood routine and renal function should be reviewed regularly to evaluate the metabolic status of the body and adjust the dose of enteral nutrition. 8.Immune-enhancing agent application: For severe cases, immune-enhancing agents can be selectively applied. 9.Prevention and treatment of intestinal failure: For SAP patients, abdominal signs and defecation should be closely observed, and changes in bowel sounds should be monitored. Give early pro-intestinal motility drugs, including raw rhubarb, magnesium sulfate, lactulose, etc.; give microecological preparations to regulate intestinal bacterial flora; apply glutamine preparations to protect the intestinal mucosal barrier. At the same time, traditional Chinese medicine, such as skin nitrate, can be applied externally. If the disease condition allows, early resumption of diet or implementation of enteral nutrition is important to prevent intestinal failure. 10.Chinese herbal medicine: single herbal medicine, such as raw rhubarb, and compound preparations, such as Qing Pancreatic Tang and Chai Shao Cheng Qi Tang, have been proven effective in clinical practice. Chinese herbal preparations achieve therapeutic efficacy by reducing vascular permeability, inhibiting macrophage and neutrophil activation, and removing endotoxin. 11.Endoscopic treatment of AP (biliary origin type): It is recommended that in conditional units, nasobiliary drainage or endoscopic sphincterotomy should be performed for suspected or confirmed AP (biliary origin type) if it meets the index of severe disease, and/or if there is cholangitis, jaundice, dilatation of the common bile duct, or if it is initially judged to be MAP, but the condition worsens during treatment. Management of complications: Acute respiratory distress syndrome is a serious complication of AP. Treatment includes mechanical ventilation and high-dose, short-course glucocorticoid application, such as methylprednisolone, and bronchoscopic alveolar lavage if necessary. Acute renal failure is treated primarily with supportive therapy, stabilization of hemodynamic parameters, and dialysis if necessary. Hypotension is associated with hyperdynamic circulation, and management includes close hemodynamic monitoring, intravenous rehydration, and vasoactive drugs if necessary. Heparin should be administered in cases of disseminated intravascular coagulation.AP with pancreatic fluid accumulation will in part develop into pseudocysts. For pancreatic pseudocysts should be closely observed, some of them will absorb on their own, and for bitter pseudocysts >6 cm in diameter with compression and clinical manifestations, puncture drainage or surgical drainage is feasible. Pancreatic abscess is an absolute indication for surgical intervention. For upper gastrointestinal bleeding, acid control agents, such as H2 receptor antagonists and proton pump inhibitors, can be applied. 13, surgical treatment: surgical intervention is considered under close observation in cases of secondary infection of necrotic pancreatic tissue. For severe cases, it is advocated that on the basis of intensive care and intensive conservative treatment, after 72h, the patient’s condition is still not stabilized or further deteriorated, which is an indication for surgical treatment, or abdominal irrigation.