Reduced Dissemination of Tumor Cells With Primary Ligation of the Inferior Mesenteric Vein in Rectal Cancer Patients.

Inclusion Criteria: 1. Age: 18-75 years; 2. Histopathologically confirmed as rectal adenocarcinoma(tumor located within 15 cm from the anal verge at colonoscopy); 3. Patients with a stage I-III rectal cancer eligible for surgery and R0 resection is expected, patients with pelvic lateral lymph nodes metastasis are ineligible; 4. ECOG score: 0-1; 5. ASA score: I/II/III; 6. Laparoscopic surgery; 7. Informed consent. Exclusion Criteria: 1. Patients who have received preoperative treatment (such as preoperative radiotherapy and chemotherapy); 2. Receiving transanal total mesorectal excision (taTME), specimen extraction through natural lumen (NOSES) ; 3. Recurrent rectal cancer; 4. Simultaneous or metachronous colorectal cancer; 5. Malignant tumors of other organs in the past 5 years or at the same time; 6. The results of preoperative physical examination and imaging examination showed that: (1) the tumor involved the surrounding organs and required combined organ resection; (2) distant metastasis; (3) could not be resected at R0; 7. Pregnant or lactating women; 8. Patients with severe mental disorder; 9. It is not suitable for patients undergoing laparoscopic surgery (such as extensive adhesion caused by previous abdominal surgery or inability to tolerate artificial pneumoperitoneum); 10. History of unstable angina pectoris or myocardial infarction in the past 6 months; 11. Have a history of cerebrovascular accident in the past 6 months; 12. Systemic administration of corticosteroids within 1 month before enrollment; 13. Taking folic acid related drugs within half a year before operation. 14. Severe cardiac insufficiency (FEV1\<50% of predicted values); 15. Emergency surgery.