Other contributing factors include hypertension, chronic obstructive pulmonary disease, hyperlipidemia, and family history. Chronic infection, inflammatory illnesses, and connective tissue disorders (eg, Marfan syndrome) can also increase the risk for aneurysm. Less frequent causes of AAA are trauma and infectious diseases, such as syphilis.1,12
In 85% of patients with femoral aneurysms, AAA has been found to coexist, as it has in 62% of patients with popliteal aneurysms. Patients previously diagnosed with these conditions should be screened for AAA.4,13,14
Diagnosis
An abdominal bruit or a pulsating mass may be found on palpation, but the sensitivity for detection of AAA is related to its size. An aneurysm greater than 5.0 cm has an 82% chance of detection by palpation.15 To assess for the presence of an abdominal aneurysm, the examiner should press the midline between the xiphoid and umbilicus bimanually, firmly but gently.12 There is no evidence to suggest that palpating the abdomen can cause an aneurysm to rupture.
The most useful tests for diagnosis of AAA are US, CT, and MRI.6 US is the simplest and least costly of these diagnostic procedures; it is noninvasive and has a sensitivity of 95% and specificity of nearly 100%. Bedside US can provide a rapid diagnosis in an unstable patient.16
CT is nearly 100% effective in diagnosing AAA and is usually used to help decide on appropriate treatment, as it can determine the size and shape of the aneurysm.17 However, CT should not be used for unstable patients.
MRI is useful in diagnosing AAA, but it is expensive, and inappropriate for unstable patients. Currently, conventional aortography is rarely used for preoperative assessment but may still be used for placement of endovascular devices or in patients with renal complications.1,12
Screening Recommendations
The US Preventive Services Task Force (USPSTF) recommends that all men ages 65 to 74 who have a lifelong history of smoking at least 100 cigarettes should be screened for AAA with abdominal US.3,18 Screening is not recommended for those younger than 65 who have never smoked, but this decision must be individualized to the patient, with other risk factors considered.
The ACC/AHA4 advises that men whose parents or siblings have a history of AAA and who are older than 60 should undergo physical examination and screening US for AAA. In addition, patients with a small AAA should receive US surveillance until the aneurysm reaches 5.5 cm in diameter; survival has not been shown to improve if an AAA is repaired before it reaches this size.1,2,19 In consideration of increased comorbidities and decreased life expectancy, screening is not recommended for men older than 75, but this too should be determined individually.3
Screening for women is not recommended by the USPSTF.3,18 The document states that the prevalence of large AAAs in women is low and that screening may lead to an increased number of unnecessary surgeries with associated morbidity and mortality. Clinical judgment must be used in making this decision, however, as several studies have shown that women have an AAA rupture rate that is three times higher than that in men; they also have an increased in-hospital mortality rate when rupture does occur. Thus, women are less likely to experience AAA but have a worse prognosis when AAA does develop.20-22
Management
The size of an AAA is the most important predictor of rupture. According to the ACC/AHA,4 the associated risk for rupture is about 20% for aneurysms that measure 5.0 cm in diameter, 40% for those measuring at least 6.0 cm, and at least 50% for aneurysms exceeding 7.0 cm.4,23,24 Regarding surveillance of known aneurysms, it is recommended that a patient with an aneurysm smaller than 3.0 cm in diameter requires no further testing. If an AAA measures 3.0 to 4.0 cm, US should be performed yearly; if it is 4.0 to 4.9 cm, US should be performed every six months.4,25
If an identified AAA is larger than 4.5 cm, or if any segment of the aorta is more than 1.5 times the diameter of an adjacent section, referral to a vascular surgeon for further evaluation is indicated. The vascular surgeon should be consulted immediately regarding a symptomatic patient with an AAA, or one with an aneurysm that measures 5.5 cm or larger, as the risk for rupture is high.4,26
Preventing rupture of an AAA is the primary aim in management. Beta-blockers may be used to reduce systolic hypertension in cardiac patients, thus slowing the rate of expansion in those with aortic aneurysms. Patients with a known AAA should undergo frequent monitoring for blood pressure and lipid levels and be advised to stop smoking. Smoking cessation interventions such as behavior modification, nicotine replacement, or bupropion should be offered.27,28