Accessory Hemiazygos Vein -

The azygos system is notoriously highly variable . Common variants include:

: If the vein is underdeveloped or absent, the left superior intercostal vein may extend further down to drain those levels. Clinical Significance Accessory Hemiazygos Vein | Complete Anatomy - Elsevier accessory hemiazygos vein

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. The azygos system is notoriously highly variable

The (also known as the superior hemiazygos vein ) is a major component of the Azygos venous system . Located in the upper left posterior mediastinum, it serves as the left-sided counterpart to the superior portion of the azygos vein, primarily draining the mid-to-upper thoracic wall. Anatomical Overview accessory hemiazygos vein