The lateral chest film as an unreliable indicator of azygos continuation of the inferior vena cava.

Recognition of azygos continuation of the inferior vena cava (AC-IVC) is necessary to prevent unnecessary surgery, to modify the approach to right heart catheterization and to avoid potentially fatal azygos ligation at the time of thoracic surgery. Absence of the inferior vena cava (IVC) shadow on the lateral chest film has been claimed to be an important feature of AC-IVC. Our findings, however, indicate that AC-IVC is frequently associated with a normal appearing IVC shadow on lateral chest film study. When the findings on frontal chest film examination suggest AC-IVC, a caval shadow on the lateral view does not exclude the diagnosis. There persists a need for further radiographic evaluation and, if necessary, angiographic confirmation. The lateral chest film does not provide reliable evidence for or against the diagnosis of azygos continuation of the inferior vena cava.