대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Azygos vein aneurysm (varix)

Radiologic Findings

Figs. 1–3. Computed tomography scans with a mediastinal window setting showing an enhancing well-defined prevertebral lesion continuous with the azygos vein.

Brief Review

In this case, the lesion was surgically confirmed as an azygos vein aneurysm (AVA) because the differential diagnoses from the initial chest computed tomography (CT) included neurogenic tumor and bronchogenic/duplication cyst.
The normal caliber of the azygos vein is < 5 mm. A venous aneurysm of the extremity is defined as a persistent isolated focal venous dilatation with a diameter 2-fold that of the normal vein. Because AVAs are usually asymptomatic, they are mostly incidentally discovered. The clinical presentation of AVAs might be related to their morphological characteristics, and large saccular aneurysms tend to present with chest symptoms because of the mass effect in the mediastinum. Sluggish blood flow through the saccular AVA allows slow sedimentation and accumulation of thrombi within the lumen, leading to partial or eventual total thrombosis and progressive gradual enlargement of the AVA.
The differential diagnoses may include thymoma, lymphoma, congenital or acquired arterial or venous lesions, neurogenic tumors, and lymphadenopathies. Occasionally, changes in lesion size when the patient is in the upright position or during a Valsalva maneuver may suggest a central venous lesion. Transesophageal ultrasonography or venography has been used for the diagnosis of AVAs. Currently, CT and magnetic resonance imaging (MRI) are considered the primary modalities for initial noninvasive assessments of AVAs. Poor enhancement of the azygos vein on CT may lead to misinterpretation of AVAs as neurogenic tumors or lymphadenopathies. An additional delayed scan with optimal venous enhancement facilitates the diagnosis of AVAs with a patent lumen. The use of CT and MRI is also helpful for evaluating thrombi within AVAs. MRI can identify blood clots or organized hematomas of various ages within the thrombosed AVA and is particularly helpful for differentiating from neurogenic tumors or lymphadenopathies. Magnetic resonance angiography can be used to depict the global morphologic features of the venous system and to distinguish a slow-flow AVA from a solid mediastinal mass.
Although surgical or various interventional treatments of AVAs have been proposed, the guidelines are not yet clear. Nonetheless, prevention of thrombus migration and pulmonary thromboembolism during surgery is important, and this can be achieved through an initial meticulous ligation of the junction of the azygos arch and superior vena cava. Conversely, conservative management may be a reasonable approach because fusiform AVAs with a patent lumen remain stable and asymptomatic for years.

Please refer to

Case ,

KSTR Imaging Conference 2015 Spring  Case 3,

References

1. Ko S-F, Huang C-C, Lin J-W, Lu H-I, Kung C-T, Ng S-H, et al. Imaging Features and Outcomes in 10 Cases of Idiopathic Azygos Vein Aneurysm. The Annals of Thoracic Surgery 2014;97:873-878
2. Savu C, Melinte A, Balescu I, Bacalbasa N. Azygos Vein Aneurysm Mimicking a Mediastinal Mass. In Vivo 2020;34:2135-2140

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