On an axial CT scan at the level of the intervertebral disc L4-L5, the structure immediately anterior to the aortic bifurcation and to the left of the inferior vena cava is:

• A Right common iliac vein
• B Left ureter
• C Superior mesenteric artery
• D Left common iliac artery ✓

Explanation

The aorta bifurcates at the level of L4 into right and left common iliac arteries. On an axial cut at L4-L5, the left common iliac artery lies immediately anterior to the vertebral body and to the left of midline. The left common iliac vein (not listed) is posterior to the corresponding artery. The left ureter crosses the left common iliac artery anteriorly at this level, making this a key landmark for ureteric injury during aorto-iliac surgery. The superior mesenteric artery originates at L1.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.