Aortic arch pseudoaneurysm

Case contributed by Frank Gaillard


Vague symptoms of breathlessness. No chest pain.

Patient Data

Age: 65 years
Gender: Female

Chest x-ray  demonstrates a large rounded opacity projecting from the mediastinum laterally on the left. Note is also made of cardiomegaly and calcific atherosclerotic disease of the arch of the aorta.


A non-contrast CT (the patient is allergic to contrast) confirms a large saccular out-pouching arising from the left side of the aortic arch.  Turbulent blood flow can be seen within the aneurysm (even on the non-contrast imaging).

Annotated image

On the frontal and lateral radiographs the outline of the aorta can be traced (red dotted line) and does not clearly blend with the mass projecting towards the right of the mediastinum (blue dotted line). 

When one looks at the CT, it is easy to understand why this is the case. Although the aorta (red dotted line) and aneurysm (blue dotted line) are in continuity, the x-ray beam are tangential to the posterior part of the arch or the aorta (red arrow) and the aneurysm (blue arrow) separately, both therefore casting a silhouette. 

Case Discussion

This case illustrates thoracic aortic aneurysm presenting as a mediastinal mass

The case also illustrates that arterial phase imaging is not required to make the diagnosis - it wasn't performed in this case because of allergy. Arterial imaging helps with diagnosis of complications and characterization. The aneurysm is probably a pseudoaneurysm resulting either from prior trauma or a penetrating atherosclerotic ulcer. 

Case courtesy of Bob Cook, MD. Western Memorial Regional Hospital Corner Brook, Newfoundland.

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