A multicenter prospective randomized controlled clinical study for the assessment of radical resection of tumors, incidence of surgical complications and difficulty of operation by preserving left colon artery in laparoscopic anterior resection of rectal cancer.

Interventions: Group 1:preservate the left colon artery;Group 2:without preservate the left colon artery
Primary outcome(s): anastomosis leak;operation time;disease free survival;Amount of bleeding
Study Design: Cohort study