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Azygous Continuation of the Inferior Vena Cava



Related narrative: Azygous Continuation of the Inferior Vena Cava

Inferior vena cava interruption is a rare congenital anomaly that is often asymptomatic and discovered incidentally. It may be associated with other cardiovascular anomalies such as dextrocardia, persistent left superior vena cava and ventricular septal defect. When associated with other anomalies, the incidence is 0.2-2.0%. It is rarer as an isolated finding (<0.3%).

The formation and remodeling of the abdominal venous drainage pattern during the embryonic period (first 8 weeks of life) involves three sets of paired veins (see narrative, frame 3-5), the post-, sub-, and supracardinals appearing and partially regressing in that order. Absence of the hepato-subcardinal anastomosis (1) and consequent rerouting of venous return results in disconnection of the hepatic venous drainage from the rest of the lower body drainage and hypertrophy of the alternate channels back to the heart. A variety of patterns of azygous continuation has been reported (2).

There are several clinical implications on finding this anomaly. The first is as a warning flag for other cardiac anomalies. Restricted venous return from the pelvis and lower extremities may predispose to venous thromboembolism. The absence of an IVC complicates venous cannulation for cardiopulmonary bypass and alternative cannulation should be planned for adequate venous drainage. The widened mediastinum seen on chest X-ray may be misinterpreted as superior mediastinal pathology such as thymoma, teratoma, substernal goiter, aortic dissection and lymphoma. CT scan or MRI should differentiate these conditions. Options for shunting for portal hypertension are affected by this condition. Ligation of an azygous vein that is the major venous return from the lower body can be lethal.


1 Trubac R, Hribernik M, Congenital interruption of the inferior vena cava with hemiazygous continuation, Scripta Medica (BRNO)-75 (6): 291-302, (12/02).

2 Tohno Y et. al., Anomalous inferior vena cava with azygos continuation in a Japanese man, Anatomical Science International, 82, 59-61 (2007)

This page was last modified on 1-May-2007.