Diagnosing Abdominal Aortic Aneurysm

Diagnostic Approach

The American College of Radiology recommends ultrasound as the definitive first-line test to distinguish normal aortic pulsation from an abdominal aortic aneurysm (AAA), with sensitivity and specificity approaching 100% 1, 2
The American Institute of Ultrasound in Medicine recommends measuring the greatest outer-to-outer (OTO) diameter of the aortic wall 1
Pre-evaluation overnight fasting reduces bowel gas interference 1, 2
Transabdominal ultrasound is the optimal screening test, providing rapid, radiation-free diagnosis with near-perfect accuracy 4, 1, 2
Ultrasound can reliably detect AAA presence in 98-99% of cases; only 1-2% are inadequate due to body habitus or bowel gas 1, 2

Aortic diameter ≥3.0 cm on any imaging modality confirms AAA diagnosis 6, 3
Ultrasound typically underestimates AAA diameter by 1-3 mm compared to CT 1, 2
Fusiform dilation (most common) versus saccular morphology (higher rupture risk at smaller sizes) 7

For AAA sizes 3.0-3.4 cm, repeat imaging every 3 years 7, 3
For AAA sizes 3.5-4.4 cm, annual surveillance is recommended 7
For AAA sizes 4.5-5.4 cm, surveillance every 6 months is recommended 7
For AAA sizes ≥5.5 cm in men or ≥5.0 cm in women, surgical referral is recommended 7