This vein’s tributaries drain from the posterior region near the iliac crest.  It usually acts as a ‘segmental ‘ vein for the L5 vertebra, and tends to run into the common iliac vein, but can also end in the inferior vena cava or inferior iliac vein.  It is connected proximally to the venous plexus behind the psoas, which subsequently drains into the azygos system.  

Its importance is that it tends to impede surgical access to the L4/5 disc and L5 vertebra from a retroperitoneal approach.  Accidental avulsion, rather than surgical division, can lead to significant and difficult to control hemorrhage.