On an axial CT of the chest at the level of the aortic arch, which structure passes posterior to the left main bronchus and anterior to the vertebral column?
- A Descending thoracic aorta
- B Oesophagus ✓
- C Thoracic duct
- D Azygos vein
Correct answer: B. Oesophagus
Explanation
The oesophagus descends through the posterior mediastinum, passing posterior to the left main bronchus and anterior to the vertebral column on axial CT. The descending aorta is slightly left and posterior. The thoracic duct ascends on the right side of the vertebral column at this level. The azygos vein ascends on the right side anterior to the vertebral bodies. This relationship is clinically relevant in explaining how left atrial enlargement displaces the oesophagus posteriorly.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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