Idiopathic dilatation of the thoracic venous system.

Isolated venous aneurysm is a rarely reported cause of a mediastinal mass. The authors describe a patient who demonstrated aneurysmal dilatation of the superior vena cava, the left innominate vein, the azygos and the hemiazygos veins and the left inferior pulmonary vein after blunt chest trauma. This case emphasizes the value of computed tomography in the diagnosis of this complex, presumably congenital entity.