Accessory Hemiazygos Vein Page

: The vein descends along the left side of the 4th to 8th thoracic vertebrae. At approximately the level of the 7th or 8th thoracic vertebra (T7-T8) , it crosses the midline to the right, passing posterior to the aorta and esophagus, to drain into the azygos vein. Tributaries : Left 4th to 8th posterior intercostal veins. Left bronchial veins (variable). Some esophageal and mediastinal veins. Anatomical Variants

The accessory hemiazygos vein is an unpaired vessel that typically resides on the left side of the vertebral column, parallel to the descending thoracic aorta.

: In rare cases (1–2%), it may drain directly into the left brachiocephalic vein .

: It may join the hemiazygos vein to form a common trunk before entering the azygos vein.

: It is formed by the confluence of the 4th through 8th left posterior intercostal veins .