Clinical Research Directory

Inclusion Criteria: 1. Able to provide written informed consent voluntarily. 2. Age ≥ 18 years old, any gender. 3. Diagnosed with severe complicated intra-abdominal infection (cIAI) within 48 hours, consistent with the 2025 expert consensus for cIAI diagnosis. Diagnosis is confirmed by clinical symptoms (fever, abdominal pain, distension, etc.), abdominal imaging (CT/ultrasound/MRI), intraoperative findings, or positive pathogen culture of abdominal drainage fluid. 4. Baseline Sequential Organ Failure Assessment (SOFA) score ≥ 2 points. Exclusion Criteria: 1. Severe immune deficiency conditions, including AIDS, prior solid organ or bone marrow transplantation, HIV infection with CD4 count \< 200 cells/mm³, long-term high-dose glucocorticoid therapy (prednisone \> 20 mg/day), ongoing chemotherapy for malignant tumors, or absolute neutrophil count \< 1000 cells/mm³. 2. Severe irreversible underlying diseases, including chronic renal failure requiring dialysis, Child-Pugh grade C liver disease, liver disease with severe portal hypertension, or acute liver failure. 3. Patients with active malignant tumors, pregnancy, or severe psychiatric disorders. 4. American Society of Anesthesiologists (ASA) physical status grade IV or above. 5. Severe coagulation disorder defined as ISTH-DIC score ≥ 5 points. 6. Critically ill patients with expected death within 48 hours after admission. 7. Known allergy to ulinastatin or any ingredients of the study preparation. 8. Any condition that, in the judgment of the principal investigator, makes the patient inappropriate for trial participation.