Radiologic Appearance of the Azygos Vein in Cardiovascular Disease

Although the usual appearances of the azygos arch on plain chest radiographs are well known, there are less common radiographic presentations which may be misconstrued as mediastinal nodes or masses. The size of the anterior azygos arch measured perpendicular to the right main bronchus should not exceed 7 mm. In the rare case of congenital aneurysmal dilatation of the azygos arch, its size may be much greater and can be confused with a mediastinal mass. Enlargement of the azygos vein can also result from increased pressure in the right ventricle or as the result of increased flow through the azygos system. Increased flow can result from congenital abnormalities or from caval obstruction.