1. To observe and measure the distance between the origin of LCA (left colonic artery，LCA) and IMA (inferior mesenteric artery，IMA) root and the distance between IMA and IMV (inferior mesenteric vein，IMV) at the origin of LCA in rectal cancer patients. Statistical analysis of intraoperative measured data, on the basis of the original anatomical relationship, to achieve anatomical localization of quantitative and accurate, for the preservation of LCA laparoscopic radical resection of rectal cancer to provide a strong anatomical basis.
2. The operation time, 253 lymph node dissection time, intraoperative blood loss, postoperative anal exhaust time, postoperative feeding time, postoperative hospital stay, postoperative ischemic colitis rate and postoperative anastomotic leakage rate of patients with laparoscopic radical resection of rectal cancer with preservation of LCA were recorded. The surgical efficacy and clinical significance of laparoscopic radical resection of rectal cancer with preservation of LCA were evaluated.

Inclusion Criteria:

• Pathological diagnosis of rectal cancer (T2-4a, N- / +, M0) ; Laparoscopic radical resection of rectal cancer and preservation of LCA Patients and their families agree to participate in the clinical study

Exclusion Criteria:

• Those who had a history of lower abdominal surgery and could not undergo laparoscopic surgery LCA vascular absence was found during operation combined with other malignant tumors pregnant or lactating patients Combined with severe mental illness Severe diseases of the blood system, coagulation dysfunction ; Preoperative assessment of heart, lung and brain function, unable to tolerate surgery.

The age was between 18 and 75 years old, and the pathological diagnosis was rectal cancer (T2-4a, N- / +, M0)