Abdominal aortic aneurysm overview

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Overview
Abdominal aortic aneurysm, also written as AAA and often pronounced 'triple-A', is a localized dilatation of the abdominal aorta, that exceeds the normal diameter by more than 50%. The normal diameter of the infrarenal aorta is 2cm. It is caused by a degenerative process of the aortic wall, however the exact etiology remains unknown. It is most commonly located infrarenally (90%), other possible locations are suprarenal and pararenal. The aneurysm can extend to include one or both of the iliac arteries. An aortic aneurysm may also occur in the thorax. The aorta below the renal arteries is the most common site for true arterial aneurysm. The abdominal aorta tends to be 2 cm in diameter, therefore a true AAA measures 3.0 cm or more. The normal diameter of one's aorta depends on the patient's age, sex, height, weight, race, body surface area, and baseline blood pressure. Aortic ectasia is a mild generalized dilatation (<50% of the normal diameter of ≤ 2.9 cm) that is due to age-related degenerative changes in vessel wall. The definition of Aneurysm is from a Greek word meaning dilatation.

Aneurysms are usually classified by their shape:
 * Fusiform aneurysms: most common type seen in the infrarenal aorta.
 * Diffuse, circumferential


 * Saccular aneurysms
 * Involve only a portion of the circumference, with a characteristic outpouching of the vessel wall.

History
The first historical records about AAA are from Ancient Rome, more precisely from the 2nd century AD, when Greek surgeon Antyllus tried to treat the AAA with proximal and distal ligature, central incision and evacuation of thrombotic material from the aneurysm. However, attempts to treat the AAA surgically were unsuccessful until 1923. In that year, Rudolph Matas (who also proposed the concept of endoaneurysmorrhaphy), performed the first successful aortic ligation on a human. Other methods that were successful in treating the AAA included wrapping the aorta with polyethene cellophane, which induced fibrosis and restricted the growth of the aneurysm. Albert Einstein was operated on by Rudolf Nissen with use of this technique in 1949, and survived five years after the operation.

Related Key Words and Synonyms:
 * AAA
 * Aortic ectasia
 * Fusiform aneurysms
 * Saccular aneurysms

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Acknowledgements
The content on this page was first contributed by: C. Michael Gibson M.S., M.D.