Background and Aims: In recent years, more and more studies have found that the preservation of left colonic artery (LCA) in laparoscopic radical resection of rectal cancer can ensure the blood supply of the proximal bowel and reduce the incidence of anastomotic leakage. However, there are several variations in the branches of the inferior mesenteric artery (IMA), the D3 lymph node dissection with LCA preservation will increase the operation difficulty and significantly prolong the operative time. This study was conducted to investigate the feasibility and safety of low ligation with LCA-preserving D3 lymph node dissection under the guidance of preoperative CT angiography (CTA).  
Methods: The clinical data of 50 patients with rectal cancer undergoing laparoscopic anterior resection with low IMA ligation and D3 lymph node dissection from January 2018 to December 2019 in the Department of Gastroenterology of the Third Affiliated Hospital of Anhui Medical University were retrospectively analyzed. All patients underwent preoperative CTA three-dimensional reconstruction of the lower abdominal vessels for identifying the types of branch vessels of the IMA.
Results: Of the 50 patients, the proportions of type I, II, III and IV of IMA branches were 48.0% (24/50), 16.0% (8/50), 34.0% (17/50), and 2.0% (1/50), respectively. The length of IMA was 1.6-4.8 cm, with an average of (3.7±0.5) cm. the incidence of Riolan artery arcade absence was 70.0% (35/50). The operation was uneventfully completed in all patients, and no open conversion was required. The time for No.253 lymph node dissection was (18.5±5.8) min on average (ranged from 12-35 min), and the number of No.253 lymph node dissection was 4.5±1.3 on average (ranged from 0-6), in which, positive lymph nodes were identified in 2 cases (4.0%), and both of them were classified a pathological stage IIIC. The total operative time was (130±26) min on average (ranged from 115–190 min), the intraoperative blood loss was (65.8±7.8) mL on average (ranged from 30–150 mL), and the total number of lymph node dissection was 17.6±4.5 on average (range from 10–39). The histological classification of the 50 patients included highly differentiated adenocarcinoma in 10 cases, moderately differentiated adenocarcinoma in 25 cases, and poorly differentiated adenocarcinoma in 15 cases, and the pTNM stage included stage I in 5 cases, stage IIB in 23 cases, stage IIIA in 15 cases a, stage IIIB in 5 cases and stage IIIC in 2 cases. The length of postoperative hospital stay was (12.5±2.3) d on average (ranged from 8–15 d). No anastomotic leakage and other serious complications occurred in all patients after surgery, and one patient had dark red blood in stool after surgery, which was improved after hemostatic therapy. All patients were discharged from hospital after recovery. Followed-up was obtained in all patients for a period of 3–26 months. liver metastases occurred in one of the two patients with positive No.253 lymph node and stage IIIC disease at 14 months after surgery, and no death occurred in the entire group. 
Conclusion: For all rectal cancer patients, routine abdominal and pelvic CTA three-dimensional reconstruction is recommended before operation. Based on the types of branch vessels of the IMA, laparoscopic anterior rectal resection with accurate low ligation, LCA preservation and D3 lymphadenectomy is safe and feasible.