Aneurysm

Aneurysm
Synonyms	aneurism
Angiography of an aneurysm in a cerebral artery. The aneurysm is the bean-shaped gray blob in the center of the image.
Classification and external resources
Specialty	Vascular surgery
ICD-10	I72
ICD-9-CM	442
DiseasesDB	15088
MedlinePlus	001122
MeSH	D000783
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An aneurysm is a localized, blood-filled balloon-like in the wall of a blood vessel. Aneurysms can occur in any blood vessel, with particularly lethal examples including aneurysms of the Circle of Willis in the brain, aortic aneurysms affecting the thoracic aorta, and abdominal aortic aneurysms. Aneurysms can arise in the heart itself following a heart attack, including both ventricular and atrial septal aneurysms.

As an aneurysm increases in size, the risk of rupture increases. A ruptured aneurysm can lead to bleeding. Aneurysms are a result of a weakened blood vessel wall, and can be a result of a hereditary condition or an acquired disease. Aneurysms can also be a for clot formation (thrombosis) and embolization. The word is from Greek: ἀνεύρυσμα, aneurysma, "dilation", from ἀνευρύνειν, aneurynein, "to dilate".

Aneurysms may be classified by type, morphology, or location.

A true aneurysm is one that involves all three layers of the wall of an artery (intima, media and adventitia). True aneurysms include atherosclerotic, syphilitic, and congenital aneurysms, as well as ventricular aneurysms that follow transmural myocardial infarctions (aneurysms that involve all layers of the attenuated wall of the heart are also considered true aneurysms).

A false aneurysm, or pseudoaneurysm, is a collection of blood leaking completely out of an artery or vein, but confined next to the vessel by the surrounding tissue. This blood-filled cavity will eventually form either thrombose (clot) enough to seal the leak, or rupture out of the surrounding tissue.

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