Cross-sectional echocardiographic diagnosis of azygos continuation of the inferior vena cava.

Azygos continuation of the inferior vena cava has importance for both the invasive diagnosis of congenital heart disease by catheterization and for surgical treatment. Cross-sectional echocardiography was used to examine 1,000 patients (1 day to 16 years, mean 3.3 years) who also had angiographic or surgical confirmation. Twenty-eight patients (3%) had azygos continuation (left 13, right 14, bilateral 1) and, in 26 patients, the hepatic portion of the inferior vena cava was absent. Azygos continuation was prospectively detected in all and was directly visualized in subcostal scans as a venous structure posterior to the aorta coursing behind the heart and not entering the inferior aspect of either atrium in 26/28 (93%). Azygos connection to the ipsilateral superior vena cava or atrium was correctly predicted in all. The inferior vena cava was visualized in all patients without azygos continuation, except one neonate with omphalocele. We conclude that cross-sectional echocardiography can accurately detect azygos continuation of the inferior vena cava and predict its side and connection.