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The largest artery in the human body is the aorta. It begins in the heart and moves oxygenated blood through the body. An aneurysm is a balloon-like bulging of an artery caused by a weakness in the vessel. Aneurysms of the aorta that occur below the kidney are referred to as an infrarenal aortic aneurysm. It is the most common type of abdominal aortic aneurysms (AAAs).
The causes of an infrarenal aortic aneurysm are not totally clear, but there are theories that suggest genetics and certain behaviors contribute to their formation. Genetics appear to be a factor largely in males. Cigarette smoking is also seen as a contributive factor, and is seen in a high percentage of patients. Other causes can be atherosclerosis, a hardening of the arteries, as well as infection and trauma.
Statistics show that over 90% of AAAs are infrarenal aortic aneurysms. AAAs can also occur at the same level as the kidneys or above them; if they are above the diaphragm, they are not considered abdominal aortic aneurysms anymore, but are referred to as thoracic aortic aneurysms. Infrarenal aortic aneurysms often extend down into the leg and lower abdomen, and into the iliac arteries.
The biggest danger in having an infrarenal aortic aneurysm, or any aneurysm, is that it will rupture. Most aneurysms gradually develop over time and can be symptomless, which is why the are so dangerous. A dissecting aneurysm is the most dangerous, and occurs when a layer of the blood vessel rips or tears, and is then followed by intense pain. Often times, the pain will subside, partially or completely, but the wall of the blood vessel is still weakened, increasing the chance of rupture. This is often mistaken for a cramp or other temporary pain.
Since most infrarenal aortic aneurysms are symptomless, they are hard to diagnose until they burst or rupture. They are often found when doing a physical exam, ultrasound or CT scan for another issue. If they aneurysm is closer to the skin it may be visible, but most aneurysms occur deeper in the body. CT scan is the most reliable test, with 100% sensitivity to aneurysms. Men between 65 and 75 are at the highest risk, and it is recommended they are screened at least once if they are smokers.
An infrarenal aortic aneurysm is treated like other aneurysms, most often with blood-thinning medications or surgery. Quitting smoking is recommended as a preventative measure for those who have small aneurysms. If an aneurysm bursts surgery is performed, but is often not successful because many patients have already lost too much blood by the time they reach the hospital. Once an aneurysm bursts, it only takes minutes for the blood loss to lead to death.