Radiological features of azygous vein aneurysm

Mediastinal masses are most commonly associated with malignancy. Azygous vein aneurysm is a very rare differential diagnosis of mediastinal mass. We report here three cases of azygous vein aneurysm including children and adult patients. In the pediatric patient it was further complicated by thrombosis and secondary pulmonary embolism. We describe the radiological features on CXR, MRI, CT, PET-CT, US and angiogram and their differential diagnosis. Imaging findings of continuity with azygous vein, layering of contrast medium on enhanced CT and dynamic MRA showing filling of the mass at the same time as the azygous vein without prior enhancement will be strongly suggestive of azygous vein aneurysm with transtracheal ultrasound being the definitive test in these patients. It is important to keep a vascular origin mass in the differential diagnosis of mediastinal masses. Also, in young healthy patients with pulmonary embolism, a vascular etiology such as azygous vein aneurysm should be carefully evaluated. This article will help the clinicians to learn about the imaging features of azygous vein aneurysm on different imaging modalities.