During a left thoracotomy for esophageal surgery, the thoracic duct is at risk. At which vertebral level does the thoracic duct cross from the right side to the left side of the vertebral column?

• A T4–T5 level
• B T1–T2 level
• C It runs entirely on the left side throughout the thorax
• D T12 to T8 ✓

Explanation

The thoracic duct enters the posterior mediastinum through the aortic hiatus at T12 with the aorta. In the lower thorax (below T5), it lies on the right side of the vertebral column between the aorta and azygos vein. At approximately T5–T4 level it crosses from right to left behind the esophagus, then continues upward on the left side of the mediastinum. It arches over the left subclavian artery at C7 level and drains into the junction of the left subclavian and internal jugular veins. This crossing makes the duct vulnerable in left-sided thoracic procedures above T5 and right-sided procedures below T5.

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

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Written and medically reviewed by the StethoPrep medical team.