FMT for the Prevention of Infectious Complications in Patients With Moderately Severe and Severe Acute Pancreatitis

Inclusion Criteria: * Age between 18 and 75 years * Diagnosed with moderately severe acute pancreatitis (MSAP) or severe acute pancreatitis (SAP) according to the Revised Atlanta Classification 2012, with CT severity index (CTSI) score \> 4 * Disease duration of 15 to 21 days * Already have a nasojejunal tube in place * No absolute contraindications to fecal microbiota transplantation * Voluntarily sign the written informed consent form Exclusion Criteria: * Concurrent severe systemic infection * Concurrent extra-intestinal organ infection requiring intervention with broad-spectrum antibiotics * Intestinal obstruction, active gastrointestinal bleeding, intestinal perforation, fulminant colitis, or toxic megacolon * Unable to tolerate enteral nutrition meeting 50% of caloric requirements due to severe diarrhea, significant fibrotic intestinal stricture, severe gastrointestinal bleeding, or high-output intestinal fistula * Pre-existing chronic organ dysfunction (heart, lung, liver, kidney, or hematologic system) prior to admission * Multiple organ dysfunction syndrome (MODS) with a confirmed duration exceeding 2 weeks * Active malignancy * Autoimmune disease or immunocompromised status (including solid organ or bone marrow transplantation, AIDS, long-term use of immunosuppressants or hormones) * Congenital or acquired immunodeficiency * Pregnancy or breastfeeding * Severe mental disorder