Azygos Vein Aneurysm Mimicking a Calcified Lymph Node.

A 66-year-old female who had been receiving treatment for a non-tuberculous pulmonary mycobacterial infection underwent enhanced computed tomography (CT). A well-circumscribed, high density nodule, measuring 12 mm in diameter, was noted in the right main bronchus (Picture 1) and it was initially considered to be a calcified mediastinal lymph node that had been caused by the mycobacterial infection. However a plain CT scan conducted 2 months later produced no abnormal findings (Picture 2). Subsequent CT angiography showed the presence of contrast material in a fusiform azygos vein aneurysm (AVA) from 12 seconds (Picture 3) after the infusion of the contrast material, suggesting that the blood stream, flowing backward from the superior vena cava, had thus become stagnated in the AVA. A three-dimensional reconstruction of the CT angiography also revealed AVA (Picture 4).

Picture 1.

Picture 2.

Picture 3.

Picture 4.

AVA is a rare condition (1), however, when it does occur, making an accurate diagnosis can be difficult because this condition may mimic the appearance of a calcified mediastinal lymph node. AVA often enlarges (1), thus posing the risk of rupture (2).

The optimal treatment for AVA remains controversial, but surgical intervention is recommended in cases complicated by rupturing, embolisms, or obstruction (3), none of which was found in our case. We therefore carefully monitored the AVA to identify any changes in its size.