Reviewed by Brian R. Robinson, MD
An Abdominal Aortic Aneurysm (AAA) is the abnormal swelling or dilation of a blood vessel in the abdomen. The aorta is the largest blood vessel in the body and is also the most common site at which aneurysms occur. Most AAAs do not produce any symptoms, although some people are able to detect a pulsing sensation in the abdomen.
AAA is usually the result of degeneration in one of the layers of the arterial wall (the media), which results in a slow and continuous expansion of the opening of the vessel. The degeneration of the media (which contains smooth muscle cells) is the result of advanced atherosclerosis. In some cases, AAAs are caused by local invasion of the arterial wall by bacteria, which gives rise to abscess formation and aneurysmal dilation of the vessel (mycotic aneurysm). In these cases, Gram-positive organisms most commonly cause mycotic aneurysm.
AAAs commonly occur in people older than age 60, and they affect men more often than women. Risk factors include high blood pressure, obesity, smoking, and family history of aneurysms. AAAs are usually detected and diagnosed by ultrasound. Less frequently occurring causes of AAA include collagen vascular diseases and congenital connective tissue disorders such as Marfan Syndrome and Ehlers-Danlos Syndrome.
Options for diagnosis include several methods of radiological evaluation, such as standard x-rays, ultrasound, CT scan, MRI, and angiography.