Emergent Care / Stabilization:
Hemodynamically unstable patient:

• Two large bore intravenous (IV) catheters
• Blood pressure control
• Pain control
• Computed tomography angiography (CTA) imaging is preferred. Testing for renal function is not necessary if there is a high index of suspicion for abdominal aortic aneurysm (AAA); there is a weak association between contrast and acute kidney injury (AKI), and the risks outweigh the benefits.
• Consultation with vascular surgery does not need to be delayed by imaging confirmation in the setting of an unstable patient with a high index of suspicion.
• Bedside ultrasound may show a positive focused assessment with sonography in trauma (FAST) examination in patients with a ruptured AAA, although it may be negative if the bleed is retroperitoneal. Ultrasound is not sensitive for rupture.
• The aorta diameter is measured from outer wall to outer wall. A common pitfall is the misinterpretation of thrombus with the outer wall of the aorta.

Diagnosis Overview:
AAA is defined as a focal, full-thickness dilation of the abdominal aorta that is 50% or more of the regular diameter, or 3 cm or larger. The abdominal aorta is retroperitoneal and lies between the diaphragm and aortic bifurcation, with about 80% of aneurysms arising infrarenally. They are most commonly degenerative in patients with atherosclerosis; 5%-10% are inflammatory and are more often symptomatic.

AAAs are most commonly diagnosed in men with a smoking history, but other risk factors for development are advanced age, other aneurysm, atherosclerotic disease, hypertension, hypercholesterolemia, chronic obstructive pulmonary disease (COPD), a family history of AAA, and White race. In women, 3 cm or larger is aneurysmal, but aortic size index (ASI, diameter in cm / body surface area [BSA]) is a better predictor of clinical events than diameter alone.

General size classifications:

• Small: < 4 cm
• Medium: 4-5.5 cm
• Large: > 5.5 cm
• Very large: ≥ 6 cm

Aneurysms expand with time but typically remain asymptomatic until rupture. Patients require serial abdominal ultrasounds following diagnosis to assess the rate of growth and risk of rupture. Rupture risk directly correlates with the size of the aneurysm. The average expansion of AAA is 0.2-0.3 cm per year. The average rate of expansion is higher in those with larger aneurysms and current smokers, which increases growth rates by approximately 20%. In the rare patient who complains of symptoms prior to rupture, abdominal, back, or flank pain are the most common presenting symptoms. Other signs and symptoms may include hematuria, gastrointestinal hemorrhage, or lower extremity ischemia. A pulsatile periumbilical abdominal mass may be found on physical examination with a bruit heard on auscultation. Risk of rupture is higher in patients with an aneurysm larger than 5.5 cm, in current smokers, and in females.

Identifying an AAA is essential, as mortality associated with rupture is up to 80% and is as high as 50%-70% in patients who make it to the hospital after a rupture. Current guidelines recommend screening for AAA in men aged 65-75 years who have ever smoked and in men or women who have a first-degree relative with an AAA.

Related topic: cystic medial necrosis