[Aneurysmal dilatation of the bulb of the azygos vein. Radiological and clinical value].

An aneurysm of the vena azygos should be taken into consideration when establishing the differential diagnosis of a tumor in the area of the right tracheobronchial angle or of an enlargement of the right upper mediastinum. Bilateral pelvic phlebography with demonstration of the retroperitoneal venous system and the azygos venous system is the only purposeful examination. Tentative diagnosis is made on the basis of the X-ray (radioscopy and general X-ray of the chest) and is supplemented by X-rays of the patient in a recumbent position (Valsalva- and Müller-test) and appropriate tomography. The most frequent cause of the azygos aneurysm in our patients was aplasia of the inferior vena cava. One patient presented an infrahepatic interruption of the inferior vena cava with azygos continuation. Phlebography of the inferior vena cava should always be performed in cases of azygos aneurysm. An abnormality of the inferior vena cava may be missing; in such cases the existence of a cardiac defect, abnormal emptying of pulmonary veins or hepatic cirrhosis should be taken into consideration. The enlargement of the azygotic arch may also occur during pregnancy. Thus an azygos aneurysm is frequently but not necessarily associated with enlargement of the azygotic arch. We saw one patient among our cases who presented aplasia of the inferior vena cava without any dilatation of the azygotic arch.