Drainage of the Accessory Hemiazygos Vein into the Left Brachiocephalic Vein

The accessory or superior hemiazigos vein (AHAzV) normally courses to the left of the thoracic spine and crosses to the right at the T7-T8 level to join the azygos vein. In ~75% of cases, there is a small connection between the accessory hemiazygos vein and the left superior intercostal vein (SICV), which normally drains into brachiocephalic vein (BCV). In about 2% of cases, this connection is large enough to allow the accessory hemiazygos vein to drain into the brachiocephalic vein. This is shown in the images above. This variant anatomy may become clinically significant as a collateral pathway in cases of venous obstruction.

This patient also has an azygos lobe and an aberrant right subclavian artery (ARSCA).

SVC, superior vena cava; Ao, aorta.

Radiology

Galwa RP, Prakash M, Khandelwal N. 16-MDCT depiction of accessory hemiazygos vein draining into the left brachiocephalic vein. Indian J Radiol Imaging 2007;17:50-1.