The SVC is subject to easy obstruction due to its thin wall and low pressure hemodynamics. Certain specific anatomic features of the SVC increase its susceptibility to obstruction as compared to the IVC.
The critical anatomical relationships causing the SVC to be vulnerable to obstruction are:
The SVC is situated in a relatively tight compartment in the right anterior superior mediastinum behind the unyielding sternum. Therefore, displacement of the SVC by a space-occupying lesion of the mediastinum is thus limited.
The SVC is completely encircled by chains of lymph nodes that drain all the structure of the right thoracic and lower left thoracic cavity. This intimate anatomic relationship places the SVC at considerable risk for compression due to enlargement of the nodes from disease.