Azygous Continuation of the Inferior Vena Cava (IVC)

Vivek David, MD
Robert D Pugatch, MD

Presentation

An asymptomatic 23-year-old woman had a routine chest radiograph, and an abnormality was noted.

Imaging Findings

Anteroposterior radiograph of the chest

CT of the chest

An anteroposterior radiograph of the chest shows a mass (arrow) at the location of the azygous vein.

Computed tomography of the chest shows a dilated azygous vein (arrows) as well as absence of the intrahepatic portion of the inferior vena cava (IVC).

Differential Diagnosis

Common causes for dilatation of the azygous vein include azygous continuation of the IVC, congestive heart failure, constrictive pericarditis, obstruction of the superior vena cava (SVC) or IVC, overhydration, pericardial effusion, portal hypertension, pregnancy, and tricuspid insufficiency. An enlarged azygous lymph node, masquerading as an enlarged azygous vein, is also a possibility.

Diagnosis

Azygous continuation of the inferior vena cava

Discussion

Azygous continuation of the IVC is a common cause of dilatation of the azygous vein. The IVC is usually interrupted at the level of the intrahepatic IVC, and blood returning from the abdomen and legs is routed through the azygous and hemiazygous veins. A useful sign in recognizing this entity is absence of the shadow of the IVC on a lateral chest radiograph. However, on occasion the hepatic veins can mimic the IVC on both frontal and lateral chest radiographs.

Azygous continuation of the IVC is associated with congenital heart defects and heterotaxy syndromes.

References

1. Kellman GM, Alpern MB, Sandler MA, Craig BM. Computed tomography of vena caval anomalies with embryologic correlation. Radiology 1990; 8: 533-555.

2. Fraser RG, Pare JAP, Pare PD, Fraser RS, Genereux GP. Diagnosis of diseases of the chest. 3rd ed. Philadelphia:WB Saunders, 1991; 2879-2885.

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