Aortic pseudoaneurysms typically occur as a result of trauma +/- intervention, a considered subset of traumatic aortic injury in the majority of cases. They can be acute or chronic.
Aortic pseudoaneurysms are contained ruptures of the aorta in which the majority of the aortic wall has been breached, and luminal blood is held in only by a thin rim of the remaining wall or adventitia.
They typically occur from focal aortic transection of which 85% are the result of penetrating trauma (gunshot or stab wounds) and 15% of cases from blunt trauma (motor vehicle accidents or falls). They also occur from non-traumatic pathologies such as penetrating atherosclerotic ulcers .
If at the level of the aortic arch, consider:
For differentiating features, see aortic pseudoaneursym versus ductus diverticulum.