To prove that early enteral nutrition after pancreaticoduodenal operation is of great significance to improve the immune response, reduce the incidence of postoperative infection and other related complications, and shorten the length of hospital stay

Arm A: Total parenteral nutrition. TPN also started from POD 1 and was delivered through a central venous catheter. Target energy of 1.5 amino acids/kg/day reached 30 kcal/kg/day.

Arm B: NJEEN was defined as providing at least 50% of the nutritional requirements through the nasojejunal tube prior to the 5th day after surgery (POD) and having no parenteral nutrition for 72 h or more.

Inclusion Criteria:

• Age between 18 and 80 years old, gender is not limited;
• All patients underwent pancreaticoduodenectomy;
• ECOG 0 ~ 2 for physical condition score;
• Imaging examination found pancreatic head, periampullary space, no distant metastasis and ascites;
• No bone marrow dysfunction;
• Those without obvious surgical contraindications;
• Expected postoperative survival ≥3 months;
• The study visit plan and other programme requirements are now available;
• Voluntary participation and signing of informed consent.

Exclusion Criteria:

• Patients with stage II and IV periampullary carcinoma of head of pancreas and periampullary carcinoma;
• Active infected persons;
• Distant metastasis or ascites were found in imaging examination;
• Patients with serious impairment of heart, liver and kidney function (grade 3 to 4, ALT and/or AST more than 3 times the normal upper limit, Cr more than the normal upper limit);
• patients with other malignant tumors or blood diseases;
• Pregnancy, planned pregnancy and lactation female patients (urine HCG >02500 iu /L, diagnosed as early pregnancy);