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ABDOMINAL AORTIC ANEURYSM OVERVIEW — An aortic aneurysm occurs when the walls of the main blood vessel that carries blood away from the heart (the aorta) bulge or dilate. Aneurysms can occur in any area of the aorta, but the abdomen is the most common site (figure 1).
Intact abdominal aortic aneurysms (AAAs) generally cause no health problems. However, large AAAs can burst, or rupture, and cause heavy bleeding into the abdomen. A ruptured AAA is a surgical emergency requiring immediate treatment. Rarely, blood clot from an AAA can break loose and lodge into the arteries of the leg, causing blockage of blood circulation and sudden and severe leg pain.
ABDOMINAL AORTIC ANEURYSM RISK FACTORS — Abdominal aortic aneurysm (AAA) is uncommon in people under the age of 60. About one person in 1000 develops an AAA between the ages of 60 and 65, and this number continues to rise with age. Screening studies show that AAAs occur in 2 to 13 percent of males and 6 percent of females over the age of 65. However, almost 90 percent of the aneurysms identified by screening are small (less than 3.5 cm in diameter) and unlikely to burst.
In addition to age, a number of other factors increase a person's risk of developing an AAA:
●Smoking markedly increases risk for AAA. The risk is directly related to number of years smoking and decreases in the years following smoking cessation.
●Males develop AAA four to five times more often than women.
●White people develop AAA more commonly than people of other ethnicities.
●People with other medical conditions, such as coronary heart disease and peripheral vascular disease, are more likely to develop AAA than people who are otherwise healthy.
●A family history of AAA increases the risk of developing the condition and accentuates the risks associated with age and gender. The risk of developing an aneurysm among brothers of a person with a known aneurysm who are older than 60 years of age is as high as 18 percent.
Screening for AAA — Doctors recommend a screening test to check for AAA in certain groups of people. These recommendations are based upon the risk of developing an AAA, which is increased in some people including older men, especially those who smoke or who have a family history of AAA.
The test used most commonly to screen for AAA is called abdominal ultrasonography. This test is painless and involves the use of a wand, which is applied to the abdomen and uses high-frequency sound waves to create an image of the abdominal aorta.
Recommendations for screening vary around the world, but in general, a screening test is recommended in the following groups:
●Males aged 65 to 75 who have ever smoked. After a single negative ultrasound, there is little benefit of repeat screening. Males older than 75 may be less likely to benefit from screening.
●Males and females aged 60 or older who have a family history of AAA. Although the risk of AAA is much lower in females than males, the risk of rupture in females is higher than in males, and some professional societies believe that one-time screening for females with risk factors is worthwhile.
SURVEILLANCE OF SMALL ASYMPTOMATIC AAA — Most abdominal aortic aneurysms (AAAs) are small when they are found by screening or after a radiologic exam (eg, ultrasound, computed tomography, magnetic resonance) was done for other reasons. Although small AAAs do not require treatment, periodic surveillance is recommended to monitor AAA size and symptoms.
People with a known AAA who do not have surveillance imaging are more likely to experience an AAA rupture. The recommended frequency of surveillance ultrasounds depends on the size of the aneurysm; very small AAAs may only require surveillance every few years, while larger ones need to be monitored yearly or even more frequently.
ABDOMINAL AORTIC ANEURYSM SYMPTOMS — Most abdominal aortic aneurysms (AAAs) are small and do not cause any symptoms. People without symptoms are usually unaware that they have an aneurysm.
Some AAAs cause a noticeable pulsation near the navel. This may not be noticed by the person but can often be detected by a health care provider during a routine physical examination. Approximately 30 percent of asymptomatic AAAs are discovered in this manner.
Some AAAs can cause abdominal or back pain. Such aneurysms are typically detected during an evaluation for pain.
Because blood can pool in the part of the aorta that is bulging, some people develop blood clots inside the aneurysm. If one of these clots breaks loose, it can end up clogging a blood vessel in one of the legs. This can lead to symptoms such as pain, numbness, or tingling in the leg. In some cases, parts of the leg or foot may even turn pale and become cool to the touch.
Most people have little warning before rupture. People who develop abdominal pain or tenderness may have had a recent increase in aneurysm size, which may predict rupture.
ABDOMINAL AORTIC ANEURYSM TREATMENT — Approximately 10,000 deaths occur each year in the United States due to abdominal aortic aneurysms (AAAs), usually because of rupture. Once rupture has occurred, the success rate of surgery is much lower than if surgery is performed electively, prior to rupture. The goal of therapy is to treat the aneurysm before rupture.
Aneurysm repair is the primary treatment for aneurysms that are symptomatic or at a high risk for rupture. Repair, however, is associated with other risks and complications. The risks and benefits of elective repair must be balanced against the risk of complications or death from an untreated aneurysm. This decision requires understanding of the usual course in people with untreated aneurysms.
Risk of rupture — The risk of rupture of small aneurysms (smaller than 4.0 centimeters) is much lower than the risk of rupture of large aneurysms (larger than 6.0 centimeters). In addition to size, the risk of AAA rupture depends upon the rate at which the aneurysm is expanding. The evidence suggests that aneurysms expand at an average rate of 0.3 to 0.4 centimeters per year (1 inch = 2.5 cm). Larger aneurysms tend to expand faster than smaller aneurysms.
There can be significant variability in the rate of expansion, both from one person to another, and for a given person from year to year. Aneurysms that expand rapidly (for example, more than 0.5 cm over six months) may be at higher risk of rupture. Many people have long periods with little change in aneurysm size. Some aneurysms, for unclear reasons, remain relatively fixed in size for a period of time and then undergo rapid expansion.
Enlargement tends to be more rapid in smokers and less rapid in people with diabetes mellitus. So far, quitting smoking is the only known way of decreasing aneurysm enlargement.
Other aneurysm complications — Other complications of AAA are less common and not as well recognized. These include:
●Inflammatory aneurysm, swelling and inflammation of the aneurysm wall that causes abdominal pain
●Aortovenous fistula, an abnormal connection between the aorta and a vein
●Primary aortoenteric fistula, an abnormal connection between the aorta and the bowel
●Blood clots or debris from the AAA that block blood flow to the legs
●Infected aneurysm
These complications can be limb- and life-threatening and, when diagnosed, indicate the need for repair.
General treatment principles — In all cases, the decision about whether and when to repair an asymptomatic AAA is based upon the risks associated with the aneurysm itself and the risks associated with the repair. Most people with an asymptomatic aneurysm less than 4.0 cm (1.6 inches) are advised not to have immediate surgery but rather to follow the aneurysm over time; this is known as watchful waiting. Usually, this involves an ultrasound examination of the abdomen every six months to three years, depending on the size of the aneurysm. (See 'Surveillance of small asymptomatic AAA' above.)
On the other hand, most people with an asymptomatic AAA greater than 5.5 cm (2.2 inches) in diameter or one that expands more than 0.5 cm within a six-month period are advised to have repair. Some doctors recommend repair of AAAs greater than 5 cm (about 2 inches) in selected females as the risk of rupture of larger aneurysms (≥5.0 cm) is greater in females than in males. Repair may also be recommended for people with AAAs that are greater than twice the size of a normal portion of the aorta.
People with an asymptomatic AAA between 4.0 and 5.5 cm should discuss their options with a physician. The best approach will depend upon the risk of repair and the person's risk of aneurysm rupture. Features influencing this decision include:
●The size of the AAA and rate at which is it expanding.
●The development of symptoms – People with AAAs that become tender to touch or are associated with abdominal or back pain may be advised to have repair even if rupture cannot be demonstrated. Other symptoms that develop that have no other cause and could be related to the aneurysm could be another reason why repair would be recommended.
●The presence of other aneurysms – People with aneurysms in other large arteries (such as the iliac, femoral, or popliteal arteries of the leg) should have their abdominal aneurysm repaired, usually before, but sometimes at the same time as these other aneurysms.
●Surgical risk – The risk of surgery varies for each individual, and the magnitude of risk may be estimated. People whose surgical risk is estimated to be high may do better with watchful waiting or less invasive aneurysm repair. (See 'Surgical risk' below and 'Medical treatment' below and 'Endovascular stent-graft' below.)
Medical treatment — Small asymptomatic AAAs that are not expanding quickly are usually left alone and watched for changes in size, most often by ultrasound examination of the abdomen every six months. A small AAA that gets to be 5.5 cm or larger, or that expands more than 0.5 cm over a six-month period of time, should probably be repaired surgically, if possible. (See 'General treatment principles' above and 'Surgical repair' below.)
People being followed with ultrasound, those awaiting repair, or those who have an AAA but whose doctor feels that surgery is too risky are watched carefully and their medical problems carefully managed. Blood pressure is carefully controlled, and cigarette smoking should be stopped.
In people who are being followed with watchful waiting, physical activity, such as walking, bike-riding, and other aerobic exercises, may reduce the risk of rupture; however, people should avoid activities like heavy lifting or other exercises that involve undue strain (such as military squats). If you would like to incorporate physical activity into your routine, ask your doctor for guidance.
People should call their doctor if they develop abdominal tenderness or back pain. These symptoms may be signs of rupture or impending rupture.
Surgical repair — AAA can be repaired either through "open surgery" or with the use of an "endovascular stent graft" (figure 2) (see 'Open surgery' below and 'Endovascular stent-graft' below). Repair of the aneurysm is recommended if it:
●Causes symptoms
●Is larger than 5.5 cm (2.2 inches) in diameter
●Is rapidly expanding, or
●Occurs along with aneurysms in the iliac, femoral, or popliteal arteries
Surgical risk — Surgery of any kind carries certain risks that vary from one person to another, depending upon the person's general state of health. The surgical risk for repair of AAA increases with age and the presence of other health conditions. As examples, people who have other heart or lung diseases and people who smoke are more likely to develop complications such as pneumonia and irregularities in their heart rates after surgery. In addition, older adults are more prone to develop problems (such as cardiac events and stroke) both during and after surgery.
Coronary heart disease is common in people with AAA. If there are other risk factors for heart disease (such as smoking, diabetes, high blood pressure), the doctor may recommend an evaluation of the heart prior to considering surgery. This evaluation may range from a simple exercise stress test to heart catheterization.
Open surgery — Open surgical correction of AAA involves removing the section of the abdominal aorta that is dilated and replacing it with a prosthesis made of synthetic material (also known as a graft) that is sutured into place (figure 2). This will allow blood to flow normally, and the artery wall is used to cover the graft. Planned or elective surgery reduces the risk of rupture of large asymptomatic AAA, and graft failure is uncommon.
Surgery is done in an operating room while the person is under general anesthesia and generally takes two to four hours, although it can sometimes take longer. After surgery, the person is taken to the intensive care unit for monitoring. Several catheters are used, including a urinary catheter (to drain the bladder), an arterial catheter (to monitor blood pressure), a central venous catheter (to monitor pressures in the heart), an epidural catheter (to give pain medicine), and a nasogastric tube (a tube from the stomach to the nose that is initially used to keep the stomach empty). People are generally able to go home after four to seven days and are able to resume normal activities in about four weeks.
Endovascular stent-graft — A less invasive surgical procedure called an endovascular aneurysm repair (EVAR) has shown success in repairing AAA. It usually involves making an incision in the groin to expose the femoral artery, placing a wire in the vessel over which a variety of specialized catheters are used to pass a folded stent-graft to the area of the AAA (figure 2). Under selected circumstances, the surgeon may instead be able to access the common femoral artery without making an incision (percutaneously). Either way, once the femoral artery is accessed, dye is injected to guide the placement of a stent-graft device into the area of the aneurysm. Once the device is correctly positioned, the stent-graft is unfolded and expanded with a balloon that pushes it up against the normal aortic wall. This type of graft is not sewn into place. Blood flows through the graft instead of the abnormally dilated aorta, which decreases the pulsations on the aortic wall.
There are less experience and fewer data regarding endovascular stent grafts than surgery, and long-term outcomes are being studied. Stent-grafts, in most cases, have become the primary mode of treatment, with approximately 80 percent of AAAs being able to be repaired with an EVAR approach. Younger people, those with underlying connective tissue diseases, and those in whom a stent-graft will not fit properly may be offered conventional open surgery.
Comparing two methods of repair — Open surgery is a little riskier in the short term, but it fixes the problem for good. Endovascular repair is less risky in the short term, but it needs to be carefully followed. That is because stent-grafts sometimes slip out of place, causing an endoleak or kinking the graft. Fixing these problems usually involves a simpler procedure than the first one. If your doctor offers you a choice between the two options, ask:
●What are the risks of each procedure for me?
●What kind of follow-up will I need with each option?
●What is likely to happen if I do not have either treatment?
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Thoracic aortic aneurysm (The Basics)")
SUMMARY — Most people with abdominal aortic aneurysms (AAAs) live healthy, symptom-free lives. The decision to undergo surgery involves weighing the risk of aneurysm rupture versus the risks and benefits of a surgical procedure. While some general guidelines are suggested based upon the aneurysm size and the rate at which it is enlarging, each treatment decision should be made on an individual basis. Patients should discuss their individual risk of surgery with an experienced healthcare provider to make an informed decision.
WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient education: Abdominal aortic aneurysm (The Basics)
Patient education: Aortic dissection (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
This topic currently has no corresponding Beyond the Basics content.
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Screening for abdominal aortic aneurysm
Clinical features and diagnosis of abdominal aortic aneurysm
Management of asymptomatic abdominal aortic aneurysm
Open surgical repair of abdominal aortic aneurysm
Endovascular repair of abdominal aortic aneurysm
The following organizations also provide reliable health information.
●Society for Vascular Surgery
(www.vascularweb.org/vascularhealth/Pages/abdominal-aortic-aneurysm.aspx)
●Vascular Disease Foundation
●National Library of Medicine
(www.nlm.nih.gov/medlineplus/healthtopics.html)
●National Heart, Lung, and Blood Institute
●American Heart Association
ACKNOWLEDGMENT — The editorial staff at UpToDate would like to acknowledge Emile R Mohler, III, MD, now deceased, who contributed to an earlier version of this topic review. UpToDate also wishes to acknowledge Dr. Mohler's work as our Section Editor for Vascular Medicine.
