In order to facilitate the estimation of prognosis and guide treatment, acute pancreatitis (AP) is often divided into light AP and severe AP (Severe acute pancreatitis, SAP). The mild type accounts for 80% of the cases, causing only very mild organ dysfunction and smooth clinical recovery. In severe cases, shock, ARDS, renal insufficiency and other multi-organ and systemic insufficiency, and even death occur, requiring active monitoring and treatment. I. Diagnosis and severity of AP The diagnosis of AP mainly relies on clinical manifestations, blood and urine amylase and CT and other auxiliary examinations. In clinical practice, it is important not only to make the diagnosis of AP, but also to distinguish between SAP and mild AP. AP has a variety of different clinical classifications because of its complex etiology, different degrees of severity, and inconsistent clinical course. The “Clinically Based Classification of AP” developed at the International Symposium on Pancreatitis in Atlanta in 1992 is a classification of AP based on pathology to the clinical one, which basically represents the current level of understanding of pancreatitis, and was revised again at the Santorini Conference in Greece in 1999. In 2000, China developed a second program (draft SAP diagnosis and treatment) based on the AP classification criteria of the International Pancreatic Conference and based on the first program for clinical diagnosis and classification of SAP in China.SAP is defined as AP with organ dysfunction, or those with local complications such as necrosis, abscess or pseudocyst, or both.SAP can be with (grade II) or without organ dysfunction (grade I), with local complications include acute pancreatic pseudocysts, acute fluid accumulation, pancreatic and peripancreatic tissue necrosis and pancreatic abscesses, which are relatively simple, objective and accurate criteria. In addition, about 25% of SAP cases develop uncontrollable multi-organ failure early in the course of the disease, with a lack of effective clinical treatment and a mortality rate of 30-60%, and most scholars refer to this SAP as fulminant acute pancreatitis (FAP). Although there were differences in the concept and diagnostic criteria of FAP, FAP has received much attention in recent years because of its aggressive onset, many complications and high mortality. With the in-depth study of SAP, scholars at home and abroad have gradually realized that the occurrence of early organ dysfunction is closely related to the waterfall-like cascade reaction caused by cytokines and other inflammatory mediators, and the role of cytokines in the early stage of SAP cannot be ignored. Isenmann and Beger reported a group of SAP patients who were hospitalized within 72 hours and developed organ dysfunction, called early severe AP ( Early severe acute pancreatitis (ESAP), with a mortality rate of 42%. A retrospective study of 209 cases of SAP admitted within 72 hours of onset at Xuanwu Hospital, Capital Medical University, showed that there were 56 cases of organ dysfunction (i.e., FAP) within 72 hours of onset, with a mortality rate of 26.7% (8/30) within three days and 53.3% (16/30) within one week. FAP has the following clinical characteristics: (1) rapid progression of the disease with progressive multi-organ dysfunction of the lungs, cardiovascular and kidneys; (2) early onset of uncorrectable hypoxemia; (3) high incidence of abdominal compartment syndrome (ACS); (4) high incidence of late complications such as pancreatic infection; (5) high CT score of pancreatic damage; (6) poor prognosis and high early mortality. High. high risk factors associated with mortality in FAP are early hypoperfusion of tissues and organs, hypoxemia and number of organ dysfunctions. The severity of AP depends on the extent of pancreatic necrosis and the presence or absence of local complications such as infection and systemic complications such as ARDS and other organ dysfunction. It is necessary to determine the severity and extent of pancreatic lesions and other organ involvement based on appropriate clinical, biochemical and imaging studies, which can help in the selection of treatment options and prognosis. Since the introduction of Ranson’s criteria in 1974, new methods have been introduced, which reflects the increasing level of understanding of AP. For example, Imrie, Bank criteria, Agarwal and Pitchumoni simplified prognostic criteria, Japanese and Hong Kong criteria, APACHE II score and Balthazar CT grading system. Inflammatory markers such as C-reactive protein, IL-1β, IL-6, IL-8, trypsinogen-activated peptide (TAP) and tumor necrosis factor (TNF) are of limited use in determining the severity of AP, and it still seems that C-reactive protein (CRP) is relatively more specific, longer lasting, and easy to perform. The ideal index to determine the severity of AP should meet the following conditions: 1, positive predictive value and high sensitivity; 2, appear in the early stage of the disease process (30 mmHg with clinical symptoms, need for timely decompression. ACS is divided into two types, one type is dominated by peritoneal fluid, accompanied by the tract, omentum, intestinal canal and posterior peritoneal edema, early laparoscopy to give abdominal irrigation, drainage, can reduce intra-abdominal high pressure, and at the same time can contain It can also dilute and drain the abdominal exudate containing pancreatic fluid and inflammatory mediators out of the abdominal cavity, reduce the systemic inflammatory response, and also reduce the inhibitory effect of abdominal exudate on intestinal motility. The other type is caused by intestinal paralysis and pneumoperitoneum of the gastrointestinal tract, and the treatment of this type of ACS should pay attention to the recovery of gastrointestinal function. Generally speaking, those with early remission of ACS will recover faster and have a good prognosis. Early identification of secondary pancreatic infection Secondary pancreatic infection includes infected pancreatic necrosis and pancreatic abscess, especially infected pancreatic necrosis often accompanied by systemic physiological disorders, high mortality, diagnosis can first dynamic CT examination, if there are bubbles can be diagnosed infection, such as no bubbles clinical suspicion of secondary pancreatic infection, CT-guided fine needle aspiration can be an early diagnosis of pancreatic infection, this method is simple, but also safe and reliable. This method is simple, safe and reliable, and is the most reliable method for early diagnosis of pancreatic infection. The puncture site can be selected via the anterior abdominal wall, lateral abdominal wall or paraspinal, and the color and properties of the puncture fluid can be observed, along with bacteriological examination including smear and culture (common, anaerobic and mycobacterial culture). In case of multiple foci care should be taken to puncture at multiple sites to avoid false negatives; and avoid the gastrointestinal tract to avoid false positives. Postoperative hyperthermia or rehyperthermia requires additional CT or puncture to look for foci of infection.