Inferior Vena Cava
The inferior vena cava (IVC, also known as the posterior vena cava) is a large diameter vein that is located posterior to the abdominal cavity and runs alongside of the right side of the vertebral column (thus making it a retroperitoneal structure), with the aorta lying laterally on the left of the IVC. Embryologically, the IVC is formed by the confluence of the left and right common iliac veins at the L5 vertebral level. It has anastomoses with the azygos vein system (running along the right side of the vertebral column) and the venous plexuses next to the spinal cord.
There are other veins that drain into the IVC along its course before it passes through the diaphragm at the caval hiatus at the T8 level. The IVC has a short intra-thoracic course before draining into the right atrium from the lower, backside of the heart.
The specific anatomical levels of the branches connected to the IVC are listed below:
- Hepatic veins (T8)
- Inferior phrenic vein (T8)
- Right suprarenal vein (L1)
- Renal veins (L1)
- Right gonadal vein (L2)
- Lumbar veins (L1-L5)
- Common iliac veins (L5)
Since the IVC is not a midline structure, there is asymmetric drainage of the vein. Notably, the gonadal and suprarenal veins drain directly into the IVC on the right side, but drain less directly into the left renal vein first, and then the IVC on the left side. All of the lumbar veins and hepatic veins usually drain directly into the IVC.
The IVC is one of the 2 large veins by which blood is returned from the body to the right side of the heart. After circulating through the body systemically, deoxygenated blood returns to the right atrium of the heart through either the superior vena cava, which drains the upper body, or the IVC that drains everything below the diaphragm, including the lower trunk, abdomen, pelvis, and lower limbs.
Inferior Vena Cava Thrombosis
Thrombosis to the IVC is often due to presence of instrumentation or from an indirect process that leads to thrombosis. IVC thromboses can be associated with:
- deep vein thrombosis (such as from a prolonged plane flight)
- IVC filters (often for the prevention of pulmonary emboli)
- liver transplantation
- catheter placement (such as in the femoral vein)
Occlusion of the IVC is a rare condition, but is considered a medical emergency. Other causes of occlusion include abdominal tumors (e.g. from colorectal cancer, renal cell carcinoma, or ovarian cancer), pregnancy, or being overweight.