Practice Essentials
Ultrasonography for the detection of abdominal aortic aneurysm (AAA) has been shown to be sensitive, specific, and relatively simple to perform.
Plummer et al demonstrated its utility as a point-of-care test in the emergency department (ED) by showing faster time to diagnosis and higher rate of survival of ruptured AAA.
Further validation studies have shown that emergency medicine (EM) residents and, by extension, appropriately trained EM physicians, are able to quickly and accurately identify AAA using ultrasound at the bedside.
It is important to remember, however, that while bedside ultrasonography can be especially useful in an unstable patient who cannot leave the ED or other acute care patient setting for computed tomography (CT) of the abdomen, it should never delay potentially lifesaving abdominal surgery when such surgery is immediately available and the diagnosis is strongly suspected.
A leaking or ruptured AAA classically presents in patients who are older than 60 years who have a history of hypertension and atherosclerosis and who experience severe abdominal, back, or flank pain after an episode of syncope.
Although AAA is more common in men than in women, the incidence of rupture is greater in women because the growth rate of AAA is significantly greater in women than in men.
Unfortunately, less than 50% of patients with ruptured AAA present with the classic triad of syncope followed by back, flank, or abdominal pain and a pulsatile abdominal mass.
Up to 30-60% of patients with AAA are initially misdiagnosed.
Be careful not to confuse AAA with more benign diagnoses such as renal colic, mechanical back pain, or diverticulitis. Maintain a high index of suspicion in patients older than 60 years who present with pain in the abdomen, back, flank, or groin.
Additionally, in at-risk patients who may present with an unrelated chief complaint, emergency ultrasonography can be a fast and accurate method for identifying patients with AAA who may benefit from follow-up or intervention.
The main disadvantages in bedside ultrasonography are that a leaking or ruptured aneurysm can be difficult to distinguish from an enlarged but nonruptured aneurysm. The aorta can also be difficult to visualize when the patient is obese or bowel gas is present.
The abdominal aorta is said to have an aneurysm when the distal aorta is dilated to a diameter larger than 3 cm.
An AAA typically enlarges at a rate of 2-8 mm/y. Because enlargement results in an increasing incidence of rupture
(eg, a 7-cm AAA has a 19-32% rate of rupture per year) and because the mortality rate is much lower with elective repair than with emergency repair (3-5% vs 50%), the general recommendation is that AAAs larger than 5.0-5.5 cm should be electively repaired.
Go to Abdominal Aortic Aneurysm and Emergent Management of Impending Rupture/Rupture of Abdominal Aortic Aneurysm for complete information on these topics.
Indications
Indications for bedside ultrasonography include the following
:
Suspicion of AAA
As a diagnostic aid in the evaluation of patients older than 60 years who present with nonspecific pain in the back, flank, abdomen, or groin
For rapid evaluation of an unstable patient in the ED or other acute care patient setting while the surgical team is assembling and resuscitation is ongoing
The U.S. Preventive Services Task Force (USPSTF) recommends the following
:
One-time screening for AAA with ultrasonography in men aged 65-75 years who have ever smoked.
Selective screening for AAA in men aged 65-75 years who have never smoked.
Current evidence is insufficient to assess the balance of benefits and harms of screening for AAA in women aged 65-75 years who have ever smoked.
Recommendation against routine screening for AAA in women who have never smoked.
Contraindications
Abdominal ultrasonography should not be performed if it would delay definitive care by means of abdominal surgery. A study of rural emergency departments in the province of Quebec found the most common reason for not using point-of-care ultrasonography was limited access to training programs.