The goal of this observational study is to learn about the biomarkers and mechanisms of severe acute pancreatitis in 30 healthy controls, 30 patients of mild acute pancreatitis, 30 patients of moderately severe acute pancreatitis, and 86 patients of severe acute pancreatitis. The main question it aims to answer are: • The relationship between changes in gut microbiota and clinical prognosis (plasma inflammatory cytokines, incidence and duration of infection in various parts, mortality rate), and the screening and validation of biomarkers that can be used for early prediction of disease severity. • Analyze the relationship between changes in blood composition and clinical prognosis (plasma inflammatory cytokines, incidence and duration of infection in various parts, mortality rate), screen and verify biomarkers that can be used for early prediction of disease severity. Blood and fecal samples from the healthy control group and diagnosed patients will be collected.

Inclusion Criteria:

Patients group:

① Age between 18 and 75 years old;

② Within 72 hours of AP onset;

③ AP patients who meet the 2012 Atlanta AP Classification and Diagnostic Criteria.

Healthy control group:

• Age between 18 and 75 years old; ② No history of acute pancreatitis; ③ Routine laboratory tests such as blood routine and fecal routine are normal.

Exclusion Criteria:

• Used antibiotics, probiotics, and acid suppressants 4 weeks before enrollment;

  • Pregnant and lactating women;

    • Hypothyroidism, nephrotic syndrome, Cushing's syndrome, AIDS;

      • Chronic pancreatitis, pancreatic cancer; ⑤ Severe history of cardiovascular and cerebrovascular diseases and organ dysfunction, such as malignant tumors, heart failure, coronary heart disease, chronic obstructive pulmonary disease, liver and kidney failure; ⑥ Unsigned informed consent form.

30 healthy controls, 30 patients of mild acute pancreatitis, 30 patients of moderately severe acute pancreatitis and 86 patients of severe acute pancreatitis, a total of 176 cases were included.