Inclusion Criteria:  Age ≥ 18 years old; diagnosis of CD; Admission time <48 hours; Subject has voluntarily signed and dated an informed consent form.  Exclusion Criteria:  Emergency surgery for intestinal fistula or abdominal abscess; Unstable vital signs or unstable hemodynamics; Pregnant or lactating women; Admission to hospital due to other critical illnesses (such as tumor, HIV, severe infections requiring ventilator or CRRT treatment); Dying patients whose life expectancy does not exceed 24 hours; Severe liver insufficiency (liver function score 11-15 or total bilirubin> 3mg/dL or tissue biopsy diagnosed as liver cirrhosis, hepatic encephalopathy, portal hypertension with history of gastrointestinal hemorrhage, etc.); Severe renal insufficiency (creatinine value is 2 times higher than the upper limit of normal); Severe metabolic diseases (such as metabolic syndrome, hyperthyroidism, etc.); Patients whose burn area exceeds 20% of the body surface area; Immunodeficiency, autoimmune disease, or receiving immunosuppressive treatment for diseases other than CD (such as organ transplantation, etc.); Those who are not suitable for body composition analysis Patients who have been selected for other clinical studies or have been selected for this study; Subjects are unwilling to participate in this study or refuse to sign informed consent.