Quantitative Ultrasound Assessment of Abdominal Cavity Space

Inclusion Criteria: * Age \> 18 years old; * Expected ICU stay ≥ 72 hours; * Meeting one of the diagnostic criteria for intra-abdominal infection: 1) Single organ infection (such as cholecystitis, appendicitis, diverticulitis, cholangitis, pancreatitis, salpingitis, etc.), which may be accompanied by or without peritonitis, even without perforation; 2) Peritonitis, classified as primary, secondary, or recurrent; 3) Intra-abdominal abscess. Exclusion Criteria: * Patients with wounds, redness, swelling, bleeding, or other conditions at the abdominal measurement points that prevent ultrasound assessment; * Patients with intra-abdominal gas accumulation that affects abdominal ultrasound imaging, making ultrasound quantitative scoring impossible; * Patients who have not undergone abdominal CT examination within 72 hours of ICU admission; * Patients who do not consent to participate in this study.