Hemiazygous continuation of a left inferior vena cava: misleading radiographic findings in chest trauma.

A widened mediastinum was found on chest radiography following blunt chest trauma. Aortography alone could not adequately determine the etiology of the radiographic findings; on computed tomography (CT) benign mediastinal widening was confirmed owing to accessory hemiazygous continuation of a left inferior vena cava (IVC), with communication to the left brachiocephalic vein through an enlarged left superior (highest) intercostal vein. This unusual anatomic variant and its radiographic findings are reviewed, as well as the complementary role of CT in the evaluation of the traumatized thoracic aorta and mediastinum.