Thoracic duct (anatomy)

The thoracic duct is the main lymphatic channel of the body that drains to the venous system from the whole of the body except the:

• right thorax
• right arm
• right head and neck

It begins as a continuation of the cisterna chyli at the level of the T12 vertebra. It passes to the right of the aorta through the aortic hiatus. It then ascends to the right of the oesophagus with the azygous vein on its left. Posteriorly are the right posterior intercostal arteries.

At the level of the fifth thoracic vertebra the duct passes superiorly and to the left, posterior to the oesophagus. It then ascends on the left side of the oesophagus into the superior mediastinum. At this point, the aorta lies anteriorly and posteriorly is the anterior longitudinal ligament of the vertebral bodies.

Superiorly, within the neck the thoracic duct passes laterally to arch over the dome of the right pleura. It passes laterally and posterior to the carotid sheath and anterior to the vertebral arteries. During this final section:

• it can divide into 2-3 branches
• it is joined by lymphatic trunks from:
  • the left side of the head - the jugular trunk
  • the left arm - the left subclavian trunk
• all the branches merge with the subclavian vein, the internal jugular vein or the left brachiocephalic vein near the intersection of all three

On route, the thoracic duct receives lymphatic efferents from:

• intercostal nodes
• anterolateral and posterior mediastinal nodes
• tracheobronchial nodes