Aneurysmal bulb dilation of the azygos vein: radiological and clinical significance.

An aneurysm of the azygos vein is usually detected in the course of routine chest X-rays. It presents as a sharply circumscribed tumor shadow in the area of the right tracheobonchial angle or as an enlargement of the upper right mediastinum. A tentative diagnosis is supplemented both by further X-rays in a supine position in combination with the Valsalva and Müller tests and by tomography. The most frequent cause of an azygos aneurysm found in our material is aplasia of the inferior vena cava. Infrahepatic interruption of the inferior vena cava with azygos continuation can also be an associated malformation. Therefore, bilateral pelvic phlebography with visualization of the retroperitoneal venous and azygos systems is mandatory for establishing the correct, complete diagnosis. We have found no concomitant hemodynamic derangements. It is important to note that under these circumstances no therapy is indicated.