The preservation of the left colic artery (LCA) in radical resection for rectal cancer depends on the classification of the inferior mesenteric artery (IMA)

D3 lymph node dissection with preservation of the left colic artery (LCA) in rectal cancer surgery is controversial in terms of reducing the incidence of postoperative anastomotic leakage (AL). We hypothesize that the existence of various variations in the inferior mesenteric artery (IMA) is an important cause. A total of 474 rectal cancer patients who underwent laparoscopic D3 lymph node dissection with LCA preservation or non-preservation between January 2019 and January 2025 were retrospectively assessed. The patients were divided into corresponding Groups I-III according to the Type I-III classification of the IMA. Within each group, patients were further split into Group A and Group B based on whether the LCA was preserved. Subsequently, differences were compared between Group IA and Group IB, Group IIA and Group IIB, and Group IIIA and Group IIIB, respectively. The incidence of postoperative AL in Group IA was significantly lower than that in Group IB ( p = 0.028), however, there were no significant differences in operation time and estimated blood loss between the two groups ( p = 0.085 and 0.123, respectively). There were no significant differences in the incidence of postoperative AL between Group IIA and Group IIB, as well as between Group IIIA and Group IIIB ( p = 0.239 and 0.259, respectively). However, Group IIA had significantly longer operation time and greater estimated blood loss than Group IIB ( p = 0.036 and 0.039, respectively), and Group IIIA also showed significantly higher values in these two indicators compared with Group IIIB ( p = 0.018 and 0.033, respectively). No significant differences were observed in length of hospital stay, lymph node retrieval, and complications between all Groups A and B cohorts. Among patients with various types of IMA, only type I patients may have a reduced incidence of postoperative AL when undergoing radical resection of rectal cancer with LCA preservation. Moreover, only in type I patients does the procedure not increase operative time and blood loss.