CT Imaging of Azygos Vein and Its Clinical Application

Objective To discuss CT manifestations of azygos vein and to evaluate the clinical significance of azygos vein abnormalities.Materials and Methods One hundred normal thoracic CT exams (study group) were randomly selected. The diameter and enhanced pattern of the azygos vein were measured and observed. Nine patients with abnormal signs of azygos vein, including portal hypertension (n=4), occlusion of SVC (n=4) and obstruction of left brachiocephalic vein trunk (n=1), were used as control group. Results In study group, the diameter of azygos vein was 6～10mm, displaying mild to moderate enhancement at 45 seconds after contrast injection, with CT values slightly lower than that of the aorta at the same level. The diameter of azygos vein over 10～12mm should be regarded as abnormal dilatation. When the enhanced CT value of azygos vein was larger than that of the aorta, it should be taken as a sign of abnormal enhancement. Conclusion Dilated azygos vein is commonly seen in the presence of collateral formation between the azygos vein and the portal vein, SVC or IVC. Abnormal enhancement of azygos vein is usually due to the obstruction of SVC, which leads to an abundant flow of contrast media directly into azygos vein. The observation of azygos vein is helpful for judging the site and extent of vascular disease, for assessing the involvement of the portal vein, SVC and IVC, and for early detecting the occult diseases.