On axial CT of the chest at the level of the aortic arch, which structure is immediately posterior to the left main bronchus?

• A Esophagus
• B Thoracic duct
• C Left recurrent laryngeal nerve
• D Descending aorta ✓

Explanation

At the level of the aortic arch on axial CT, the descending aorta lies immediately posterior to the left main bronchus. The esophagus is posterior and slightly to the right of the descending aorta. The thoracic duct ascends posterior to the esophagus. This anatomical relationship is surgically critical during left pneumonectomy and during operations on the esophagus where the descending aorta and left main bronchus are key landmarks.

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

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Written and medically reviewed by the StethoPrep medical team.