Cohort Study on Nutritional, Metabolic, and Volumetric Assessment After Pancreaticoduodenectomy

Inclusion Criteria: * Adults aged between 18 and 80 years; * Histologically or radiologically confirmed diagnosis of resectable periampullary malignant neoplasms (e.g., pancreatic head adenocarcinoma, ampullary carcinoma, distal cholangiocarcinoma, duodenal adenocarcinoma); * Candidates for elective pancreaticoduodenectomy (either classic Whipple or pylorus-preserving technique), performed by the institutional surgical team following standardized protocols; * ECOG Performance Status ≤2; * Adequate cardiopulmonary function to undergo major surgery, as assessed preoperatively; * Ability and willingness to provide written informed consent. Exclusion Criteria: * Previous pancreatic surgery; * Pancreaticoduodenectomy performed outside the study institution; * Evidence of unresectable disease, distant metastases, or local tumor recurrence at baseline imaging or intraoperative assessment; * Active inflammatory or autoimmune diseases (e.g., rheumatoid arthritis, lupus, inflammatory bowel disease); * Active malignancy other than periampullary cancer, or history of non-pancreatic cancer within the past 5 years; * Use of systemic immunosuppressive therapy (e.g., corticosteroids \>10 mg/day prednisone equivalent, chemotherapy, biologics); * Diagnosed malabsorption syndromes unrelated to pancreatic disease; * Severe hepatic dysfunction or severe renal impairment (eGFR \<30 mL/min/1.73m²); * Pregnancy or breastfeeding; * Refusal or inability to attend scheduled follow-up visits within 6…