Hemiazygos vein

Dr Henry Knipe et al.

The hemiazygos vein is the asymmetric counterpart to the azygos vein and forms part of the azygos venous system

Gross anatomy


The hemiazygos vein is formed by the confluence of the left ascending lumbar and left subcostal veins. 


The hemiazygos vein enters the thorax either through the aortic hiatus or directly through the diaphragmatic crura. It then courses superiorly to the left of the midline in the posterior mediastinum, adjacent to the thoracic vertebrae until the level of T8 or T9 vertebral bodies, where it crosses the midline anteriorly to the vertebral column to drain into the azygos vein. 

  • left posterior 8th-11th intercostal veins
  • left superior phrenic vein 
  • left renal vein (occasionally)
  • IVC (occasionally)

Variant anatomy

Anatomy: Thoracic
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Article information

rID: 26573
System: Chest, Vascular
Section: Anatomy
Synonyms or Alternate Spellings:
  • Hemiazygous vein
  • Hemi azygos vein
  • Hemi azygous vein

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Cases and figures

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    Case 1: appearance on CTPA
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