Posterior Abdominal Wall Drainage:
- 5 pairs of lumbar veins drain the posterior abdominal wall.
- The 5th lumbar vein drains into the iliolumbar vein.
- The 3rd and 4th lumbar veins drain directly into the inferior vena cava.
- The 1st and 2nd lumbar veins drain into the ascending lumbar veins.
Thoracic Wall Drainage:
- 11 intercostal veins travel within the intercostal spaces with the arteries and nerves.
The intercostal veins drain into the internal thoracic vein.
The first intercostal vein typically drains directly into the brachiocephalic vein.
Second and third intercostal veins which merge to form the superior (aka, supreme) intercostal vein.
4th - 11th posterior intercostal veins drain into the azygos system.