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What is Abdominal Aortic Aneurysm: Causes, Symptoms, Diagnosis, and Treatment

Definition and Overview

An abdominal aortic aneurysm (AAA) is a bulge or swelling in the section of the aorta (the longest and largest artery that runs from the heart through the chest and abdomen) that passes through the abdomen. It begins when the walls of the aorta weaken. The pressure of the blood pumping through the weakened area causes it to slowly dilate and bulge like a balloon.

Small AAAs normally do not produce symptoms and are often found incidentally when a person undergoes diagnostic or imaging tests for a different medical condition. Those that grow too large, on the other hand, can rupture and cause serious life-threatening internal bleeding. A ruptured abdominal aortic aneurysm is the 15th leading cause of death in the United States and the 10th leading cause of death in men older than 55.

Ruptured AAAs also increase the risk of blood clot formation, which can break off and travel to other parts of the body where they can cause partial or complete blockage. If they get stuck in arteries that supply blood to the brain or heart, they can cause a stroke or heart attack.

Causes of Condition

What causes abdominal aortic aneurysm to form is not fully understood. Some doctors believe that clogged arteries (atherosclerosis) cause the aortic wall to weaken and the blood pressure in the affected area to increase. Other possible causes include:

  • Inherited connective tissue disorders

  • Blood vessel inflammation (arteritis)

  • Genetics or heredity - A person with inherited defects, such as Ehlers-Danlos and Marfan syndromes, has an increased risk of developing the condition.

  • Infection of the aorta - In rare cases, bacterial or fungal infections may cause AAA.

  • Injury or trauma to the aortic wall

Factors that can increase one’s risk of AAA include:

  • Anastomotic disruption

  • Diabetes

  • Family history of AAA - A person with a first-degree relative with AAA has a 25% risk of developing the condition.

  • Gender - The condition is more common in men than women.

  • High blood pressure - A person with a weakened aortic wall is more likely to develop AAA if he or she is also suffering from high blood pressure.

  • Old age - The condition is often diagnosed in people over the age of 55.

  • Personal history of aneurysms - A person who had other types of aneurysms in other parts of the body has an increased risk of developing AAA.

  • Smoking

  • Race - AAA is more common in Caucasians than any other race.

Key Symptoms

Small abdominal aortic aneurysms typically do not produce any noticeable symptoms. However, if an AAA enlarges and ruptures, it can cause sudden onset of severe abdominal, flank, and back pain. A ruptured AAA is also closely associated with massive internal bleeding that can lead to shock, abdominal distension, and a pulsating abdominal mass. Other symptoms include:

  • Nausea

  • Vomiting

  • Low blood pressure

  • Fast pulse

  • Hypotension

Ruptured AAA is one of the most fatal surgical emergencies with an overall mortality rate of up to 90%.

Who to See and Types of Treatments Available

Most AAAs that are not causing symptoms are discovered through standard imaging tests performed during a routine health exam or for an unrelated medical condition. Large, symptomatic AAAs, on the other hand, are diagnosed with the following tests and procedures:

  • Ultrasound

  • Computed tomography (CT) scan

  • Angiogram

  • Transesophageal echocardiography

Such procedures reveal the size, shape, and precise location of the aneurysm.

Treatment for AAAs is not always necessary. Small aneurysms that are highly unlikely to rupture are closely monitored. Patients are advised to undergo ultrasound or CT scan every six months to ensure that the condition is not progressing. This approach, which is referred to as active surveillance, is recommended if the benefits of treatment do not outweigh the possible risks. To ensure that the condition does not worsen, the patient is advised to:

  • Make lifestyle changes, such as eating a healthy diet and exercising regularly

  • Avoid smoking

  • Take medications to control medical conditions that can worsen the condition, such as high blood pressure and diabetes

However, treatment is immediately initiated if:

  • The size of the aneurysm is between 1.9 and 2.2 inches

  • The aneurysm is growing fast

  • The patient is experiencing severe symptoms

The goal of treatment is to prevent the abdominal aortic aneurysm from rupturing either with traditional open surgery or endovascular repair techniques. Doctors decide on the best approach to use based on the shape, location, and size of the aneurysm, as well as the patient’s overall health and age.

  • Traditional surgical approach - Involves removing and replacing the damaged section of the aorta with a synthetic tube. The procedure, which requires making a large incision in the abdomen, is performed under general anaesthesia and takes between three and five hours. Most patients are required to stay in the hospital for up to 10 days and are allowed to return to their normal activities within six and twelve weeks after surgery. Open surgical repair often produces good long-term results.

  • Endovascular repair - The treatment of choice for abdominal aortic aneurysms because it is as effective as open surgery but is minimally invasive. It uses small incisions in the groin area where a guide wire is inserted and threaded until it reaches the damaged part of the aorta. A stent-graft is then left in place to reinforce the weakened part of the aortic wall and to serve as a new passageway for blood flow. The procedure takes only one to three hours and patients are discharged from the hospital after a few days. Many are able to return to their normal activities within two to six weeks after the procedure.

Follow-up care is crucial after surgery. Patients need to undergo periodic physical exams and imaging tests to ensure that their condition is improving and that the synthetic graft is not leaking.

The survival rate for patients with an unruptured AAA is generally good. However, more than 50% of people whose AAA ruptures before getting access to emergency care do not survive.

References:

  • Svensjö, S., et al. “Low prevalence of abdominal aortic aneurysm among 65-year-old Swedish men indicates a change in the epidemiology of the disease.” Circulation 124.10 (2011): 1118-1123.

  • Guirguis-Blake JM, Beil TL, Senger CA, Whitlock EP. Ultrasonography screening for abdominal aortic aneurysms: a systematic evidence review for the U.S. Preventive Services Task Force. Ann Intern Med. 2014 Mar 4. 160(5):321-9.