To evaluate the feasibility and clinical significance of preserving left colonic artery in rectal cancer surgery.The investigators will focus on the effect of preserving left colonic artery during radical resection of rectal cancer on anastomotic leakage and oncology efficacy.

The investigators performed three-dimensional (3D) reconstruction to investigate the vascular anatomy, including the inferior mesenteric artery (IMA) and left colic artery (LCA),to help make pre-operative strategies of rectal cancer surgery.The investigators will preserving the left colonic artery during rectal cancer surgery and evaluate its feasibility and clinical significance.The investigators will focus on the effect of preserving left colonic artery during radical resection of rectal cancer on anastomotic leakage and oncology efficacy.

Inclusion Criteria:

1. Pathological biopsy confirmed adenocarcinoma of the rectum；
2. Preoperative assessment of tolerance to surgery without major organ dysfunction；
3. Patients must be able to understand and voluntarily sign written informed consent；
4. The surgical method is laparoscopic or robotic anterior rectal cancer resection.

Exclusion Criteria:

1. The patient cannot tolerate the operation；
2. Refusal to sign informed consent；
3. Patients with distant metastasis of rectal cancer；
4. The surgical method was changed to miles or Hartman;
5. Unable to complete the follow - up

Patients who underwent laparoscopic or robotic anterior rectal resections carried out by two surgeons at Daping Hospital.