Accessory Hemiazygos Vein -

: In rare cases (1–2%), it may drain directly into the left brachiocephalic vein .

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

: 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 : In rare cases (1–2%), it may drain

: It may join the hemiazygos vein to form a common trunk before entering the azygos vein. : In rare cases (1–2%)

: It is formed by the confluence of the 4th through 8th left posterior intercostal veins .