Which structure lies to the left of the thoracic duct in the posterior mediastinum?

Which structure lies to the left of the thoracic duct in the posterior mediastinum?

• A. Aorta
• B. Left subclavian artery
• C. Pulmonary trunk
• D. Vagus nerve

Answer: (A)

In the posterior mediastinum, the thoracic duct runs behind the esophagus and typically lies between two major vessels: the aorta on its left and the azygos vein on its right. Because of this arrangement, the structure that lies to the left of the thoracic duct is the aorta. The left subclavian artery is higher up in the mediastinum and not a constant left neighbor of the duct here; the pulmonary trunk is more anterior and superior in this region; and the vagus nerve travels with the esophageal plexus but is not a consistent left-adjacent structure to the thoracic duct in this position.

In the posterior mediastinum, the thoracic duct runs behind the esophagus and typically lies between two major vessels: the aorta on its left and the azygos vein on its right. Because of this arrangement, the structure that lies to the left of the thoracic duct is the aorta. The left subclavian artery is higher up in the mediastinum and not a constant left neighbor of the duct here; the pulmonary trunk is more anterior and superior in this region; and the vagus nerve travels with the esophageal plexus but is not a consistent left-adjacent structure to the thoracic duct in this position.