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.
