3. Identify the azygos system of veins.
Passing upward along the right side of the vertebral bodies, note the azygos vein. It should be joined by a hemiazygos vein and an accessory hemiazygos vein on the left side. On the left side, identify the hemiazygos vein as it passes behind the aorta to join the azygos vein. Notice its tributaries joining the posterior intercostal spaces. Also look for an accessory hemiazygos vein as it passes behind the aorta and joins the azygos on the left side. Look also for the right superior intecostal vein joining the azygos system. On the left side the upper intercostal veins drain into the left superior intercostal vein that drains into the left brachiocephalic vein.
