There are two vena cavae in humans. The superior vena cava (SVC) is formed by the junction of the right and left brachiocephalic veins, crosses the pericardium, and empties into the top of the right atrium. The inferior vena cava (IVC) is formed by the convergence of the right and left iliac veins, crosses the diaphragm, and empties into the bottom of the right atrium. The SVC is an intrathoracic vessel, whereas the IVC is essentially intraabdominal, with a short, practically notional intrathoracic course. The two venae cavae supply the venous return to the right heart: about 25% from the SVC and 75% from the IVC (1,2).
