An Abdominal Aortic Aneurysm (AAA) develops in the section of the aorta located in the abdomen that supplies blood to the lower part of the body. An AAA can be categorized as small, 3.0-3.9 cm in width, medium, 4.0-5.4 cm, or large at more than 5.4 cm. Large AAAs are the most dangerous due to the potential for rupture and are usually treated with surgery or endovascular repair. AAA can continue to grow, so even if categorized as small and medium, they need to be periodically monitored to determine the rate of growth.
Who is at Risk?
According to Medscape, 15,000 deaths per year are caused by AAAs. The highest risk patients are men aged 65-75 years who have ever smoked (at least 100 cigarettes). Smoking is the most often predictor associated with AAA, with a direct correlation between the number of cigarettes consumed and the increasing risk of AAA.
Women aged 65-75 who have ever smoked or have a family history of AAA have a lower risk than the male demographic but may still benefit from POCUS screening. Patients with certain conditions such as atherosclerosis, vascular inflammation, high cholesterol/blood pressure, previous aneurysms, bacterial fungal infection in the aorta, and obesity may also be at risk and benefit from POCUS scanning for AAA.
AAA can be asymptomatic or can include any of the following:
- Sudden pain in the abdomen or back
- Pain that migrates from the abdomen back down to the pelvis, legs, or buttocks
- Pulsating sensation near the naval
- Dizziness and shortness of breath
- Increased heart rate
The primary method of screening is abdominal ultrasound. This imaging modality has a high sensitivity (94%-100%) and specificity (98%-100%) for detecting AAA. POCUS is an easy test to perform and is non-invasive, so most at-risk patients are generally good candidates to be screened. It is highly accurate in detecting and determining the size of an AAA. High-risk patients should have a one-time routine screening, and lower-risk individuals should be selectively screened. Patients who have never smoked and have no family history of AAA may not benefit from routine screening.
The entire abdominal aorta is scanned. The average diameter of a male’s aorta is 1.7 cm, and in a female, 1.5 cm. The measurement is taken in the upper, mid and lower abdominal aorta. The diameter of the aorta is recorded in both the transverse and mid longitudinal plane. The diameter of the aortic is measured. If the diameter of the aorta is more than 3.0 cm, AAA is diagnosed. Aneurysms can grow up to 25 cm in diameter.
The shape of an aneurysm can be fusiform or saccular. The saccular aneurysm is rarer than the fusiform type.
Small and medium AAAs that are determined to be low risk of rupture are monitored with periodic screening to assess their growth rate. The risk of rupture is 11% or less in AAAs less than 5.9 cm in diameter. There is no standard interval for scanning these low-risk AAAs, and patient history should be used to inform a recommended interval. If the patient currently smokes, the recommendation would be to stop immediately.
AAAs greater than 5.5 cm or have shown a growth increase of 1 cm per year in diameter are considered high risk of rupture. Endovascular aneurysm repair is the most common treatment option for intact and unruptured AAAs.
Timely detection of AAAs can result in treatment to avert potentially fatal outcomes. Since POCUS screening is non-invasive, inexpensive, and highly sensitive in diagnosing AAAs, routine screening of men 65 years and older who have high levels of blood cholesterol, a family history of cardiovascular disease, or a history of smoking can reduce the rate of mortality.