Abdominal Aortic Ultrasound for AAA Screening
For suspected abdominal aortic aneurysm (AAA, commonly called "triple A"), order a dedicated abdominal aortic ultrasound that specifically measures the infrarenal aorta in anteroposterior diameter. 1
Key Ordering Specifications
The ultrasound must be a dedicated examination of the abdominal aorta, not a general abdominal ultrasound. 1 The study should include:
- Leading-edge to leading-edge anteroposterior (AP) diameter measurements at the proximal, mid, and distal infrarenal aorta 1
- Common iliac artery assessment with diameter measurements 1
- Complete longitudinal evaluation of the full aneurysm extent when present 1
- Bilateral kidney imaging to assess size, parenchymal thickness, and hydronephrosis 1
- Documentation of mural thrombus if present, as this correlates with expansion rates 1
Diagnostic Thresholds
An AAA is defined as infrarenal aortic diameter ≥3.0 cm. 1 Normal infrarenal aorta measures up to 2 cm in AP diameter, with ectasia defined as 2.0-2.9 cm. 1 The threshold is approximately 10% smaller in women than men. 1
When Ultrasound Is Insufficient
If the ultrasound inadequately defines the AAA (approximately 5% of cases, particularly with juxtarenal or suprarenal extension), CT imaging is recommended for complete assessment. 1 MRI is a reasonable alternative when CT is contraindicated or to reduce radiation exposure. 1
Important Technical Considerations
- Ultrasound sensitivity is 95% with near 100% specificity for AAA detection 1
- Ultrasound tends to underestimate aneurysm size by approximately 4 mm compared to CT angiography 1
- Color Doppler is not necessary for screening or surveillance examinations 1
- Interobserver reproducibility should be within 4 mm for reliable surveillance 1
Common Pitfall
Do not order a "general abdominal ultrasound" or "complete abdominal ultrasound" when AAA is suspected. These studies may not include the specific measurements and complete aortic assessment required for AAA diagnosis and surveillance. 1 The order must specify dedicated abdominal aortic ultrasound or AAA screening ultrasound.
Note: The question appears to reference "Triple A" which in vascular medicine refers to Abdominal Aortic Aneurysm (AAA), not Triple A syndrome (Allgrove syndrome), which is an entirely different genetic condition involving adrenal insufficiency, achalasia, and alacrima. 2, 3, 4 The evidence provided and this answer address AAA screening, which is the appropriate interpretation given the imaging context of the question.