A pseudoaneurysm, also known as a false aneurysm, is a hematoma that forms as the result of a leaking hole in an artery. Note that the hematoma forms outside the arterial wall, so it is contained by the surrounding tissues. Also it must continue to communicate with the artery to be considered a pseudoaneurysm. This must be distinguished from a true aneurysm which is a localised dilatation of an artery including all the layers of the wall. A pseudoaneurysm is also different from an arterial dissection, which is a separation of the layers of the arterial wall, and may be associated with later aneurysm formation. Distinctively, in a pseudoaneurysm, the hole in the arterial wall is generally the consequence of a vascular injury. By opposition, true aneurysms and dissections are usually the consequence of an arterial wall congenital or acquired deficiency, for example by means of atherosclerosis.
Femoral pseudoaneurysms may complicate up to 8% of vascular interventional procedures. Small pseudoaneurysms can spontaneously clot, while others need definitive treatment.
A pseudoaneurysm may also occur in a chamber of the heart following myocardial damage due to ischemia or trauma. A pseudoaneurysm of the left ventricle is a potentially lethal complication from a myocardial infarction.