Inferior vena cava
The inferior vena cava is formed by the union of the right and left common iliac veins in front of the L5 vertebra, to the right of the midline. Its path ascends to the right of the aorta, resting on the lumbar vertebrae, right psoas muscle and right sympathetic trunk. The right renal, suprarenal and lumbar arteries cross behind it, and the inferior vena cava then passes posterior to the epiploic foramen and right lobe of the liver to enter the thorax through the caval opening of the diaphragm. The tributaries to some extent correspond to branches of the abdominal aorta with important exceptions:
- the venous return from the gastrointestinal tract and spleen is to the portal venous system.
- the left suprarenal, gonadal and inferior phrenic veins join the left renal vein.
- the lumbar veins, in addition to being tributaries of the inferior vena cava, are connected by an ascending lumbar vein on each side which forms an anastomotic channel with the azygos vein on the right side and the hemizygos vein on the left.