Azygous vein

Azygos Vein

The azygos vein and its tributaries.

The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It forms part of the posterior mediastinal structures at the level of the fourth thoracic vertebra.

Structure

The azygos vein is formed by the union of the right subcostal and right ascending lumbar vein. It enters the thorax through the aortic hiatus in the diaphragm at the level of the twelfth thoracic vertebra. The vein ascends in the posterior mediastinum to the right of the thoracic aorta.

Function

The azygos vein serves to drain the thoracic wall and upper lumbar region. It also serves as a major collateral pathway for venous return from the lower part of the body, in case of obstruction of the inferior vena cava.

Clinical significance

Anomalies of the azygos vein are rare but can be significant in the context of cardiothoracic surgery. Enlargement of the azygos vein can be a sign of superior vena cava obstruction.

See also

• Hemiazygos vein
• Accessory hemiazygos vein
• Superior vena cava
• Inferior vena cava