Anatomic variations of inferior mesenteric artery and left colic artery evaluated by 3-dimensional CT angiography: Insights into rectal cancer surgery - A retrospective observational study.

OBJECTIVE: To demonstrate the clinical applicability of 3-dimensional CT angiography (3D-CTA) in evaluating the anatomic variations of inferior mesenteric artery (IMA) and left colic artery (LCA), to help make pre-operative strategies of rectal cancer surgery.

METHODS: 188 patients with abdominal and pelvic contrast-enhanced CT scan were retrospectively enrolled and 3D-CTA was reconstructed. The origin and branching patterns of IMA, tracking patterns of LCA, intersectional patterns among IMA, LCA and inferior mesenteric vein (IMV) were examined, and their associations with clinical features were analyzed.

RESULTS: The origin of IMA was located 42.1 ± 7.7 mm above iliac artery bifurcation, 64.4% within the area of the 3rd lumbar vertebra. 47.3% of LCA arose independently from IMA, 27.1% arose at the root of sigmoid artery (SA), 20.7% shared a common trunk with SA while 4.8% of LCA was absent. As for track of LCA before anastomosis with marginal artery, 53.2% went straight upward while medial to the inner border of left kidney (Type A), 27.1% traveled diagonally across left kidney (Type B) and14.9% went infero-laterally to the lower border of left kidney (Type C). Short IMA trunk was independently associated with type A LCA and lower site of IMA origin. At the horizontal level of IMA origin, 29% of the LCA went distant from IMV, while 71% (21% medial, 50% lateral) were mutually close, and the close type was independently associated with type A LCA.

CONCLUSION: Preoperative understanding of the vascular variations and the mutual relationship among LCA, IMA and IMV could be obtained by 3D-CTA, which would further help surgeons to set detailed plans for laparoscopic rectal cancer surgery.