The decision to screen for AAA is difficult to make because it would expose many previously undiagnosed small aneurysms that are unlikely to rupture, resulting in needless disease labelling ( 35). Magnetic resonance angiography is probably more accurate than CT, but is more expensive and not universally available ( 34). Disadvantages of CT scanning compared with USG include increased cost, requirement for contrast, exposure to radiation with repeated scans and limitation of accuracy in localizing the aneurysm neck in some cases compared with contrast angiography ( 33). CT angiography is also essential in tailoring stent grafts in cases for which endovascular treatment is indicated.
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Although USG is generally preferred, multislice CT angiography can be used for serial monitoring of aneurysm size. It also assesses the shape of the aneurysm with more comprehensive anatomical details of the mesenteric and iliac arteries, and also provides better imaging of suprarenal aneurysms ( 33). Disadvantages of abdominal USG are that it is operator dependent and, in 1% to 2% of cases, overlying bowel gas or obesity hinders proper imaging of the abdominal aorta ( 32).ĬT scanning evaluates the abdomen in more detail in patients with a specific abdominal complaint. Thrombus or echodense calcifications in or adjacent to the aortic wall may also be seen and both are quite common. USG has excellent test characteristics for diagnosing and following an AAA.
However, they are not reliable because some aneurysms do not have sufficient calcification to be detected.Ībdominal USG is considered the screening modality of choice for AAAs because of its high sensitivity of 95% to 100% and a specificity of nearly 100%, as well as its safety and relatively low cost ( 30, 31). An AAA may also be found with plain x-rays showing some calcification in the wall of the aneurysm. The sensitivity of physical examination for the identification of an AAA ranges from 22% to 96%, and even an experienced physician may miss palpating an AAA in the presence of obesity or abdominal distention ( 29).Īn asymptomatic AAA is often discovered incidentally because of the performance of abdominal USG, CT or magnetic resonance imaging for other purposes. However, the physical examination has considerably variable interobserver sensitivity for detection of AAAs. The accuracy of the clinical examination is tremendously reduced by obese body habitus and small aneurysm size ( 28). Large aneurysms in thin people are easy to detect. The vascular examination should include abdominal auscultation because the presence of a bruit may indicate aortic or visceral arterial atherosclerotic disease, or rarely an aortocaval fistula (machinery murmur). Physical examination may reveal a pulsatile, expansile mass at or above the umbilicus. Approximately 30% of asymptomatic AAAs are discovered as a pulsatile abdominal mass on routine physical examination. The diagnosis of an AAA should ideally be made before the development of clinical symptoms to prevent rupture. Management options for patients with an asymptomatic AAA include reduction of risk factors such as smoking, hypertension and dyslipidemia medical therapy with beta-blockers watchful waiting endovascular stenting and surgical repair depending on the size and expansion rate of the aneurysm and underlying comorbidities. The United States Preventive Services Task Force recommended that men between the age of 65 to 75 years who have ever smoked should be screened at least once for AAAs by abdominal ultrasonography. The decision to screen for AAAs is challenging. Abdominal ultrasonography is considered the screening modality of choice for detecting AAAs because of its high sensitivity and specificity, as well as its safety and relatively lower cost.
It can also present with abdominal pain or complications such as thrombosis, embolization and rupture. The majority of AAAs are asymptomatic and are detected as an incidental finding on ultrasonography, abdominal computed tomography or magnetic resonance imaging performed for other purposes. The likelihood that an aneurysm will rupture is influenced by the aneurysm size, expansion rate, continued smoking and persistent hypertension. The risk of abdominal aortic aneurysms (AAAs) increases dramatically in the presence of the following factors: age older than 60 years, smoking, hypertension and Caucasian ethnicity. An arterial aneurysm is defined as a focal dilation of a blood vessel with respect to the original artery.
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