Accessory hemiazygos vein

Andrew Murphy and Dr Henry Knipe et al.

The accessory (or superior) hemiazygos vein forms part of the azygos system and along with the hemiazygos vein, it is partially analogous to the right-sided azygos vein. It drains the left superior hemithorax. 

Gross anatomy

Origin and course

The accessory hemiazygos vein is formed by the confluence of the middle left posterior intercostal veins. It descends to the left of midline, adjacent to the thoracic vertebrae and crosses posteriorly to the aorta at the level of T7-8 to drain into the azygos vein. It normally anastomoses with the left superior intercostal vein.

  • left 4th-8th posterior intercostal veins
  • left bronchial veins (variable)

Variant anatomy

  • drains via a common trunk with the hemiazygos vein into the azygos vein
  • forms a common trunk with the hemiazygos vein that passes anterior to the aorta called the interazygos vein 2
  • drains directly into the left brachiocephalic vein (rare) 2
Anatomy: Thoracic
Share article

Article information

rID: 26595
System: Vascular, Chest
Section: Anatomy
Synonyms or Alternate Spellings:
  • Superior hemiazygos vein

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1
    Drag here to reorder.
  • Case 1: appearance on CTPA
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.