Accessory hemiazygos vein

Accessory hemiazygos vein
Diagram showing completion of development of the veins (accessory hemiazygos vein visible at center-left)
The venae cavae and azygos veins, with their tributaries.
Details
Drains to	Hemiazygos vein, azygos vein
Latin	Vena hemiazygos accessoria, vena azygos minor superior
Dorlands /Elsevier	v_05/12850481
Anatomical terminology []

The accessory hemiazygos vein is a vein on the left side of the vertebral column that generally drains the fifth through eighth intercostal spaces on the left side of the body.

The accessory hemiazygos vein varies inversely in size with the left superior intercostal vein.

It receives the posterior intercostal veins from the 4th, 5th, 6th, and 7th intercostal spaces between the left superior intercostal vein and highest tributary of the hemiazygos vein; the left bronchial vein sometimes opens into it.

It either crosses the body of the eighth thoracic vertebra to join the azygos vein or ends in the hemiazygos.

When this vein is small, or altogether absent, the left superior intercostal vein may extend as low as the fifth or sixth intercostal space.