Left superior intercostal vein
Origin and course
The left superior intercostal vein forms by the union of the 2 to 4 left posterior intercostal veins. It courses superiorly to the left of the midline, arches posteriorly lateral to the aortic arch to drain into the left brachiocephalic vein.
It typically communicates with the accessory hemiazygos vein.
- left 2 to 4 posterior intercostal veins
- may not communicate with the accessory hemiazygos (25%)
- left azygos (or hemiazygos) lobe may be caused by an aberrant left superior intercostal vein (analogous to the azygos lobe)
- hemiazygos and accessory hemiazygos veins may drain directly into the left brachiocephalic vein via the left superior intercostal vein
- may be enlarged in the presence of congenital azygos, hemiazygos or accessory hemiazygos vein absence (rare)