Abdominal aortic aneurysms are bulges (dilations) in the wall of the aorta in the part that passes through the abdomen (abdominal aorta).
Abdominal aortic aneurysms typically slowly expand and sometimes rupture.
Aneurysms may cause a pulsing sensation in the abdomen and, when they rupture, cause deep, excruciating pain, low blood pressure, and death.
Doctors often detect an aneurysm during an examination or imaging procedure that is done for another purpose.
Medications to lower blood pressure are given, and aneurysms that are large or growing are repaired by either surgery or a procedure to insert a stent inside the aneurysm.
(See also Overview of Aortic Aneurysms and Aortic Dissection.)
The aorta is the largest artery of the body. It receives oxygen-rich blood from the heart and distributes it to the body through smaller arteries that branch off of it. The abdominal aorta is the part of the aorta that passes through the abdominal cavity.
Abdominal aortic aneurysms may occur at any age but are most common among men aged 50 to 80 years. Abdominal aortic aneurysms may run in families and are more likely to occur in people who have high blood pressure, especially those who also smoke. About 20% of abdominal aneurysms eventually rupture.
Smoking is a major risk factor for development of abdominal aortic aneurysms, especially in men.
Often an abdominal aortic aneurysm is caused by weakening of the wall of the artery as a result of atherosclerosis. Infection in the wall of the aorta, which may be a complication of heart valve infection (endocarditis) or body-wide infection (sepsis), and blood vessel inflammation (vasculitis) may also cause the artery wall to weaken. (See figure Where Do Aortic Aneurysms Occur?)
Symptoms of Abdominal Aortic Aneurysms
People who have an abdominal aortic aneurysm often have no symptoms, but some people become aware of a pulsing sensation in their abdomen.
The aneurysm may cause pain, typically a deep, penetrating pain mainly in the back because of compression of the spine or nearby structures. The pain can be severe and is usually unrelenting if the aneurysm is leaking.
When an aneurysm ruptures, the first symptom is usually excruciating pain in the lower abdomen and back and tenderness in the area over the aneurysm. If the resulting internal bleeding is severe, a person may rapidly go into shock. A ruptured abdominal aortic aneurysm is often fatal and is always fatal if not treated.
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Diagnosis of Abdominal Aortic Aneurysms
Ultrasonography or computed tomography (CT) of the abdomen
Pain is a useful clue, but pain often does not occur until an aneurysm is large or about to rupture. However, many people with aneurysms have no symptoms and are diagnosed by chance when a routine physical examination or an imaging procedure (such as x-rays, CT, or ultrasonography) of the abdomen is done for another reason.
Doctors may feel a pulsating mass in the center of the abdomen. With a stethoscope placed on the middle of the abdomen, doctors may hear a whooshing sound (bruit) caused by turbulence as blood rushes past the aneurysm. However, in people with obesity, even large aneurysms may not be detected. Rapidly enlarging aneurysms that are about to rupture commonly hurt or feel tender when pressed during an abdominal examination.
Occasionally, an abdominal x-ray detects an aneurysm that has calcium deposits in its wall, but this test provides little other information. Other diagnostic tests are more useful for detecting aneurysms and determining their size. Usually, ultrasonography can clearly show the size of an aneurysm. If an aneurysm is detected, ultrasonography may be repeated every few months to determine if and how quickly the aneurysm is enlarging.
CT of the abdomen, particularly if done after a contrast agent is injected intravenously, can determine the size and shape of an abdominal aortic aneurysm more accurately than ultrasonography but exposes the person to radiation. Magnetic resonance imaging (MRI) is also accurate but may not be available as quickly as ultrasonography or CT.
Screening ultrasonography for abdominal aortic aneurysms, even if people have no symptoms, is sometimes recommended for certain people older than 65 years, such as men who have smoked and have a family history of an abdominal aortic aneurysm.
Treatment of Abdominal Aortic Aneurysms
A procedure to replace the aneurysm with a synthetic graft
Abdominal aortic aneurysms that are less than 2 inches (5 centimeters) wide rarely rupture. The only treatments required may be antihypertensive medications to lower blood pressure, statins to lower cholesterol, aspirin to reduce risks related to atherosclerosis, and smoking cessation. For people who smoke, quitting is very important.
Imaging procedures are done to estimate the rate of enlargement and determine when repair will be necessary. At first, procedures are done every 3 to 6 months, then at various intervals, depending on how quickly the aneurysm is enlarging.
Aneurysms that are wider than about 2 to 2½ inches (5 to 5.5 centimeters) may rupture, so doctors usually recommend repair, unless repair is too risky for a particular person. In people with Marfan syndrome, aneurysms are at a higher risk of rupturing at narrower diameters, and so an aneurysm may be repaired earlier, when its diameter at the aortic root (part of the aorta nearest the heart) is about 1½ inches (4.5 cm) wide.
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Repair consists of inserting a synthetic tube (graft) to replace the aneurysm. There are two approaches:
Traditional surgery
Endovascular stent graft repair
With traditional surgery, a general anesthetic is given, and an incision is made from below the breastbone to just below the navel. The graft is stitched into place in the aorta, the walls of the aneurysm are wrapped around the graft, and the incision is closed. This procedure takes 3 to 6 hours, and the hospital stay is usually 5 to 8 days. The risk of death during surgery to insert a graft is about 2 to 5% but can be higher if a person has other serious medical conditions.
Endovascular stent graft repair is a less invasive approach that is used in more often than traditional surgery. A regional (epidural) anesthetic, which causes loss of sensation only from the waist down without loss of consciousness, is used. Through a special puncture needle, a long, thin guide wire is threaded through the femoral artery into the aorta to the aneurysm. A tube (catheter) containing the stent graft (which resembles a meshed, collapsible straw) is guided over the wire and positioned inside the aneurysm. Then the stent graft is opened, forming a stable channel for blood flow. This procedure takes 2 to 5 hours, and the hospital stay is usually 1 to 2 days.
The choice of aneurysm repair technique depends on many factors, including the person's age and general health and the anatomy of the aorta and the aneurysm. In general, open surgery may be used for younger and healthier people because the results may last longer in patients who are expected to live at least 10 years. The endovascular stent grafting procedure is used for older people or for people who are in poor health and who might not survive an open surgical procedure.
Treatment of a ruptured abdominal aortic aneurysm
Rupture or impending rupture of an abdominal aortic aneurysm requires emergency open surgery or placement of an endovascular stent graft. The risk of death during an emergency repair of a ruptured aneurysm is about 50%. The risk of death may be lower (20 to 30%) with endovascular stent graft placement. When an aneurysm ruptures, the kidneys may be affected because their blood supply is disrupted or because blood loss results in shock. If kidney failure develops after repair of a ruptured aneurysm, the chances of survival are very poor.
