<Tr> <Td> L2 </Td> <Td> right gonadal vein </Td> </Tr> <Tr> <Td> L1--L5 </Td> <Td> lumbar veins </Td> </Tr> <Tr> <Td> L5 </Td> <Td> common iliac veins </Td> </Tr> <P> Because the inferior vena cava is located to the right of the midline, drainage of the tributaries is not always symmetrical . On the right, the gonadal veins and suprarenal veins drain into the inferior vena cava directly . On the left, they drain into the renal vein which in turn drains into the inferior vena cava . By contrast, all the lumbar veins and hepatic veins usually drain directly into the inferior vena cava . </P>

The superior and inferior vena cava drain blood into the