Abdominal Aortic Aneurysm

What is an aneurysm?An aneurysm is an area of a localized widening (dilation) of a blood vessel. (The word "aneurysm" is borrowed from the Greek "aneurysma" meaning "a widening").
What is an aortic aneurysm?An aortic aneurysm involves the aorta, one of the large arteries that carries blood from the heart to the rest of the body. The aorta bulges at the site of the aneurysm like a weak spot on an old worn tire.
What are the thoracic and abdominal aorta?The aorta is first called the thoracic aorta as it leaves the heart, ascends, arches, and descends through the chest until it reaches the diaphragm (the partition between the thorax and abdomen). The aorta is then called the abdominal aorta after it has passed the diaphragm and continues down the abdomen. The abdominal aorta ends where it splits to form the two iliac arteries that go to the legs.
Where do aortic aneurysms tend to develop?Aortic aneurysms can develop anywhere along the length of the aorta. The majority, however, are located along the abdominal aorta. Most (about 90%) of abdominal aneurysms are located below the level of the renal arteries, the vessels that leave the aorta to go to the kidneys. About two-thirds of abdominal aneurysms are not limited to just the aorta but extend from the aorta into one or both of the iliac arteries.

What shape are most aortic aneurysms?Most aortic aneurysms are fusiform. They are shaped like a spindle ("fusus" means spindle in Latin) with widening all around the circumference of the aorta. (Saccular aneurysms just involve a portion of the aortic wall with a localized out pocketing).
What's inside an aortic aneurysm?The inside walls of aneurysms are often lined with a laminated blood clot that is layered like a piece of plywood.
Who is most likely to have an abdominal aortic aneurysm?Abdominal aortic aneurysms are most common after age 60. Males are 5 times more likely than females to be affected. This means men over 60 are at highest risk to develop an abdominal aortic aneurysm. Approximately 5% of men over age 60 develop an abdominal aortic aneurysm.
What is the most common cause of aortic aneurysms? The most common cause of aortic aneurysms is "hardening of the arteries" called arteriosclerosis. At least 80% of aortic aneurysms are from arteriosclerosis. The arteriosclerosis can weaken the aortic wall and the pressure of the blood being pumped through the aorta causes expansion at the site of weakness.
What are other causes of aortic aneurysms?
Other causes of aortic aneurysms include:
Cigarette smoking - cigarette smoking not only increases the risk of developing an abdominal aortic aneurysm, the chance of aneurysm rupture (a life threatening complication of abdominal aneurysm) is also more common among active smokers.
High blood pressure
High serum cholesterol
Diabetes mellitus
Genetic - There is a familial tendency to developing abdominal aortic aneurysms. Individuals with first-degree relatives having abdominal aortic aneurysms have a higher risk of developing abdominal aortic aneurysm than the general population. They also tend to develop the aneurysms at younger ages and have a higher tendency to suffer aneurysm rupture than individuals without family history.
There are also rare inheritable genetic diseases of connective tissue (tissue that make up the wall of the aorta) such as Ehlers-Danlos syndrome and Marfan's syndrome that can lead to the development of aortic aneurysms.
Post-traumatic: After physical trauma to the aorta.
Arteritis (inflammation of blood vessels) as occurs in Takayasu disease, giant cell arteritis, and relapsing polychondritis.
Mycotic (fungal) infection that may be associated with immunodeficiency, IV drug abuse, heart valve surgery.

What are the symptoms of an abdominal aortic aneurysm?
Most abdominal aortic aneurysms produce no symptoms (they are asymptomatic). They are often incidentally discovered when abdominal ultrasounds and/or CAT scan studies are ordered for other conditions. When they produce symptoms, the most common symptom is pain. The pain typically has a deep quality as if it is boring into the person. It is felt most prominently in the lower back region and lower abdomen. The pain is usually steady but may be relieved by changing position. The person may also become aware of an abnormally prominent abdominal pulsation.
Abdominal aortic aneurysm can remain asymptomatic or produce mild to moderate symptoms for years. However, a rapidly expanding abdominal aneurysm can cause sudden onset of severe, steady, and worsening lower back and lower abdominal pain. A rapidly expanding aneurysm is also at imminent risk of rupture. Actual rupture of an abdominal aneurysm can cause sudden onset of back and abdominal pain, sometimes associated with abdominal distension, a pulsating abdominal mass, and even shock (severe low blood pressure due to massive blood loss).
How is an abdominal aortic aneurysm diagnosed clinically?
Careful feeling of the abdomen by the doctor may reveal the abnormally wide pulsation of the abdominal aorta. This is characteristically felt on both sides of the aorta which is in the midline of the abdomen. Note that even large aneurysms can be very difficult to detect on physical examination in overweight people. Aneurysms on the verge of rupture and that are rapidly enlarging, are often tender.
What tests help in the diagnosis of an abdominal aortic aneurysm?
In about 90% of the cases, X-rays of the abdomen show calcium deposits in the aneurysm wall. But plain x-rays of the abdomen cannot determine the size and the extent of the aneurysm. Ultrasonography usually gives a clear picture of the size of an aneurysm. Ultrasound has about 98% accuracy in measuring the size of the aneurysm, and is safe and noninvasive. But ultrasound cannot accurately define the extent of the aneurysm and is inadequate for surgical repair planning. CT scanning of the abdomen, particularly with intravenous contrast dye, can be highly accurate in determining the size and extent of the aneurysm, and its relation to the renal arteries. But CAT scan requires the use of radiation and carries a risk of dye reaction (such as worsening of kidney function) when intravenous dye is used with CAT scanning. In patients with kidney diseases, the doctor may order a MRA (magnetic resonance angiography), which is a study of the aorta and the other arteries using MRI scanning. Both CAT scan and MRA are highly accurate in determining aneurysm size and extent, and are often sufficient in providing enough information in surgery planning. Only in selected special situations where abdominal aortography has to be performed before surgery. Aortography shows the origin of the major blood vessels arising from the aorta and reveals the size and extent of any aneurysm. But aortography is invasive and requires the insertion of a catheter through the groin into the aorta and use of contrast dye administered into the aorta.

What is the natural history of abdominal aortic aneurysms?
The natural history of abdominal aortic aneurysms depends on their size and the speed of expansion. Rupture of aneurysms is uncommon when they are less than 5.5 cm wide and are expanding slowly. Rupture is far more common in aneurysms that are over 5.5 cm wide and are expanding rapidly(>0.5 cm/year). Surgical repair is therefore usually recommended for aneurysms over 5.5 cm wide.
What are the complications with an abdominal aortic aneurysm?
Rupture is a feared problem. Rupture of an abdominal aneurysm is a catastrophe. It is highly lethal and is usually preceded by excruciating pain in the lower abdomen and back, with tenderness of the aneurysm. Rupture of an abdominal aneurysm causes profuse bleeding and leads to shock. Death may rapidly follow. Half of all persons with untreated abdominal aortic aneurysms die of rupture within 5 years. Abdominal aortic aneurysms are the 13th leading cause of death in the U.S.
Peripheral embolization of clot within the aneurysm can occur when a piece of clot comes loose and travels further out in the arterial system. This clot fragment can lodge in a smaller artery and block the flow of blood. Infection of aneurysms can occur from turbulent blood flow from the rough inner surface of the affected aorta.
How are abdominal aortic aneurysms repaired?
The goal of surgical treatment of abdominal aortic aneurysm is to prevent aneurysm rupture. Traditionally, repair of aortic aneurysms has been surgical. The surgery has usually consisted of opening the abdomen, removing (excising) the aneurysm, and sewing a synthetic (Dacron) tube in its place.
More recently, "minimally invasive" procedures have been devised using stent grafts that can be guided to the site of the aneurysm without the need to cut open the abdomen. The first stent graft was installed in 1991 by Dr. Juan Parodi in Argentina.
A stent graft developed by Dr. Thomas Fogarty at Stanford is a Dacron tube inside a collapsed metal-mesh cylinder. To install the stent, a small incision is made in the thigh to gain access to the femoral artery. The stent, about 6 inches (15 cm) long, is guided inside a long plastic capsule through the arteries to the lower aorta. Once the stent is in place, the holding capsule is removed. Activated by heat, the stent expands like a spring and becomes anchored to the artery wall. The by-passed aneurysm then is shielded from the blood flow and typically shrinks over time. According to a U.S. national multi-center study reported by Dr. Christopher Zari from Stanford in 1998, the "minimally invasive" installation of the stent graft carries a lower rate of complications and permits people to get back on their feet faster than traditional open surgery.

What is done if an abdominal aortic aneurysm threatens to rupture?
Threatened rupture of abdominal aneurysms is a surgical emergency. The operative risk for a ruptured aneurysm is about 50%. If kidney failure occurs after surgery, the prognosis (outlook) is particularly poor.
What is the medical management (non-surgical management) of abdominal aortic aneurysm?
For patients who are not surgical candidates (for example for patients with aneurysm smaller than 5 cm); medical treatment to prevent aneurysm expansion and rupture include:
Stopping cigarette smoking
Controlling high blood pressure
Lowering high blood cholesterol
Some doctors may consider medications called beta blockers, such as propanolol (Inderal), which has been shown in animal and some human studies to slow the rate of aneurysm expansion
Close monitoring of the aneurysm size with ultrasound or CAT scan every 6 to 12 months (sooner in high risk patients)
Abdominal Aortic Aneurysm At A Glance
An aneurysm is an abnormal area of localized widening of a blood vessel.
The aorta bulges at the site of an aneurysm like a weak spot on a worn tire.
Aortic aneurysms are typically spindle-shaped and involve the aorta below the arteries to the kidneys.
Five percent of men over 60 develop an abdominal aortic aneurysms.
The most common cause of an aneurysm is arteriosclerosis.
Abdominal aortic aneurysms often do not cause symptoms. If they do, they may cause deep boring pain in the lower back or abnormally prominent abdominal pulsation.
X-rays of the abdomen and other radiologic tests can be used in diagnosing an aneurysm.
Rupture of an aortic aneurysm is a catastrophe.
Repair of the aneurysm can be done by surgery or by installation of a stent graft.