An aneurysm is a weak point in a blood vessel wall, most commonly in an artery. Blood pressure tends to push the weakened section of an arterial wall outward, forming a balloon-like projection. This condition by itself isn't especially harmful, but the artery is prone to rupture. A ruptured aneurysm breaks the artery and allows uncontrolled bleeding to occur, which can be fatal.
Aneurysms can form in different places. The most common type of aneurysm is an abdominal aortic aneurysm (AAA). The aorta is the body's largest artery, carrying blood from the heart to every organ except the lungs. It leaves the heart flowing upwards in the chest, makes a U-bend, and flows down the spine from the chest to the abdomen. Several branches leave the aorta in the abdomen, going to the kidneys, liver, and intestines. These branch points are prime sites for aneurysms.
Other locations for aneurysms are:
- the bottom of the brain – the most common type of cerebral (brain) aneurysm is called a berry aneurysm
- the chest – a thoracic aortic aneurysm
- the most common type of thoracic aneurysm is the aneurysm of the ascending aorta (between the heart and the U-bend)
Aneurysms tend to occur in older Caucasian men; women are less at risk. By age 80, over 5% of Caucasian men have developed an aneurysm. People of African descent rarely develop aneurysms.Abdominal aortic aneurysms occur in 5% to 10% of men 65 and older and in approximately 1% of women 65 and older. These numbers gradually increase with age. They rarely occur in people under age 55. As many as 70% of people who experience a ruptured abdominal aortic aneurysm die from it before reaching the hospital.