An aneurysm, or bulge in the diameter of an artery, can occur in any artery of the body when its outer wall weakens. Abdominal aneurysm actually refers to the weakening and bulging of the abdominal segment of the aorta, the major artery that leaves the heart. Patients whose abdominal aortic aneurysms (AAA) rupture almost inevitably die without immediate surgery, according to the Merck Manual, but if found early, most aneurysms can be successfully treated with medicines or surgery.
Size
An aneurysm occurs when an artery bulges to 50 percent greater than its normal size. For the abdominal segment of the aorta, a circumference of greater than 3 cm indicates an aneurysm, according to the Merck Manual. An AAA involves all three layers of the artery wall. The risk of rupture increases with the size of the abdominal aortic aneurysm. According to the Merck Manual, your risk for rupture is 0 percent per year if the AAA is less than 4 cm in diameter, but the risk increases to 30 to 50 percent if the AAA is 8 cm or more in diameter.
Prevalence
Abdominal aortic aneurysms affect between 0.5 and 3.2 percent of people, according to the Merck Manual. Men are three times more likely to develop an AAA than women and whites have more AAA's than blacks. Older people have a higher risk for AAA that peaks between 70 and 80 years of age.
Symptoms
People with an AAA usually have no idea they have an aneurysm until a medical exam for some other purpose reveals its presence. Some patients experience a steady deep pain in their lower back and some notice an unusually strong pulse in the abdomen. A doctor might be able to feel an AAA as a pulsing mass in the abdomen.
According to the National Heart Lung and Blood Institute, most AAA's grow slowly without causing any symptoms. Rapidly expanding AAA's that are about to rupture can cause tenderness. If the AAA ruptures, and the patient does not die immediately, symptoms include low blood pressure, a racing heartbeat and sudden severe pain in the lower back or abdomen.
Causes
Aging, smoking and atherosclerosis (hardening and narrowing of the arteries) contribute to the likelihood of an AAA. Genetic conditions such as Marfan syndrome or Ehlers-Danlos syndrome can cause AAA in unusually young patients because their arteries and other connective tissues are weak. Inflammation of blood vessels or untreated infections can cause AAA too.
Treatment
A small AAA might not require treatment. Instead your doctor might want to closely monitor the size of the AAA over time and eliminate risk factors such as high blood pressure and atherosclerosis. According to the Merck Manual, surgery is recommended for AAA over 5 cm in circumference because at that size the risk for rupture increases to 5 to 10 percent. The surgeon will graft a synthetic material over the bulge or insert a stent up through the artery in the femur to reinforce the weak part of the abdominal aorta.
