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.