An aneurysm is a bulge in the wall of a blood vessel. When an aneurysm forms in the body's largest artery—the aorta—it is called an aortic aneurysm. Though most aneurysms occur in the aorta, they can form in any artery, anywhere in the body. Aortic aneurysms are typically found in the lower part of the aorta, the part that runs through your abdomen. These are called abdominal aortic aneurysms. If an aneurysm occurs in the part of the aorta that runs through your upper chest, it is called a thoracic aortic aneurysm.
If any aneurysm becomes large, there is a danger that it will break open, or rupture. When an aortic aneurysm ruptures, internal bleeding occurs and may cause death. More than 15,000 American die each year due to ruptured aortic aneurysms.
An aortic aneurysm develops from a weakness in the wall of the aorta. This weakness usually occurs due to a gradual degeneration (thinning) of the vessel wall. In many cases, the exact causes of an aortic aneurysm are not known. Factors thought to lead to aneurysms include:
Commonly called "hardening of the arteries," atherosclerosis is often found in association with an aortic aneurysm. Atherosclerosis is frequently observed in the artery wall of aneurysm patients, though there is much debate as to whether or not atherosclerosis actually causes most aneurysms. In atherosclerosis, a substance called plaque forms on the lining of the blood vessel wall, weakening the wall. Plaque is formed when cholesterol, fibrous cells, and/or calcium deposit themselves in the vessel wall. This process can form stenosis (a "narrowing") or, some believe, can lead to aneurysm formation.
- Genetic susceptibility:
Researchers have found that in male patients with an aortic aneurysm, there is a 20-30% incidence of aneurysms in first order male relatives.
- High blood pressure:
High blood pressure puts stress on the walls of the aorta. Over many years, this stress can lead to bulging of the blood vessel wall. This is a leading factor in development or enlargement of aneurysms of the thoracic aorta. If a patient has an aneurysm, it is very important to control his or her blood pressure, as a lack of blood pressure control can lead to rupture of the aneurysm.
- Cystic medial necrosis:
In this condition, the medial (middle) layer of the blood vessel wall degenerates, resulting in a weakening of the supporting structure of the blood vessel wall. This occurs with certain rare, inherited conditions such as Marfan syndrome and Ehlers-Danlos syndrome.
- Mycotic aneurysm:
This condition occurs when bacteria spread in the blood stream and invade the blood vessel wall, causing the artery to weaken and dilate. Often the bacteria attach to an area of previous damage. Although rare today, the advanced form of the sexually transmitted disease syphilis was a common cause of this condition in the early part of the twentieth century. Infections are rare causes of aortic aneurysms.
- Inflammatory aneurysm:
Inflammatory conditions or vasculitis may produce inflammation in the blood vessel wall itself. If the inflammation is not reversed, it eventually weakens the wall of the aorta, producing an aneurysm. This is also a rare cause of aortic aneurysms.
Injury to the chest or abdomen, as in a car wreck or bad fall, can damage an area of the aorta. Such a damaged area may bulge and create what is called a "false" aneurysm.
Although diabetes damages blood vessels by leading to premature, accelerated atherosclerosis, it is not currently believed to be a cause of aortic aneurysms.
Most aneurysms cause no symptoms and are discovered on an x-ray, CT scan, ultrasound, or by a physician during a physical exam. When an aneurysm leaks or expands, the patient may complain of:
- Chest pain
- Abdominal pain
- Back pain
- A tearing or ripping pain
- A pulsating bulge or a strong pulse in the abdomen
When the aorta widens, blood clots (called thrombi) are likely to form. If a piece of a blood clot breaks off, it travels through the circulatory system until it lodges somewhere. The clot can cut off blood flow to any area of the body. Symptoms depend on which part of the body is deprived of blood. The most common location for a clot to form is in the leg. A clot can also break off and go to the kidneys, causing kidney failure.
If a ruptured aneurysm occurs there can be sudden death. If internal bleeding is slow, symptoms, such as the following, may occur:
- Rapid heart beat
- Loss of consciousness (fainting)
- Bruising of the abdomen or flank
- Abdominal, flank, or groin pain
- Routine physical examination (not reliable in obese patients)
- Abdominal ultrasound:
Abdominal aortic aneurysms are safely and easily diagnosed by a simple ultrasound scan that can be performed in a few minutes, without risk or discomfort.
- Abdominal CT (computed tomography) scan:
A CT scan (often called a CAT scan) shows much more detail of the organs, blood vessels, and other structures inside the body using a series of x-rays.
Ultrasounds can be quickly and easily performed in our vascular laboratory. Please see the Vascular Diagnostic Tests web page for more information.
Surgery is usually required to repair an aortic aneurysm, but modern, catheter-based technologies using endovascular grafts have made treatment less invasive in many cases. The combination of early diagnosis and modern treatment of aortic aneurysms can save numerous lives lost due to aneurysm rupture each year.
For more information on treatment options, please see our web page devoted to the treatment of aortic aneurysms.