Can duplex ultrasound (ultrasound using Doppler and conventional ultrasound) erroneously report a lesion when there is none in patients suspected of having iliac artery stenosis?

Can Duplex Ultrasound Falsely Report Iliac Artery Stenosis?

Yes, duplex ultrasound can erroneously report iliac artery stenosis when none exists (false positive), with a positive predictive value of only 60-89% in the iliac segment, meaning that 11-40% of positive findings may be incorrect. 1

Understanding the Specificity Problem

While duplex ultrasound has excellent overall specificity of 95% for detecting >50% stenosis in peripheral arterial disease 2, the iliac arteries present unique technical challenges that reduce diagnostic accuracy:

Technical Limitations Causing False Positives

• Bowel gas and vessel tortuosity significantly diminish accuracy in the iliac arteries by obscuring visualization, which is particularly common in this anatomic location 3

• Dense calcification can obscure flow assessment and lead to overestimation of stenosis severity when interpreting velocity criteria 3

• Operator dependence is a critical factor, as duplex ultrasound reliability fundamentally depends on the sonographer's expertise 2

The Actual Performance Data

Research demonstrates the false positive problem clearly:

• Studies show duplex ultrasound has a positive predictive value of only 60-89% for iliac segments, meaning positive findings require confirmation 1

• In contrast, the negative predictive value is 97-100%, meaning a negative study reliably excludes significant disease 1

• One study found sensitivity of 93% but specificity of only 91%, with a positive predictive value of just 75% 4

Clinical Approach to Avoid Misdiagnosis

When duplex ultrasound suggests iliac artery stenosis, obtain CT angiography for confirmation before proceeding with revascularization. 3, 1

Recommended Diagnostic Algorithm

• Use duplex ultrasound as initial screening combined with ankle-brachial index (ABI), recognizing its limitations in the iliac region 3, 1

• Obtain CT angiography when duplex suggests significant stenosis and intervention is being considered, as CTA has 90-100% sensitivity and specificity for detecting iliac stenoses 3, 1

• Reserve catheter angiography with pressure measurement for cases where non-invasive imaging shows borderline stenosis or when clinical presentation doesn't match imaging findings 3

Critical Pitfall to Avoid

• Never rely on resting ABI alone for iliac disease, as isolated iliac stenosis frequently presents with normal resting ABIs but becomes apparent only with exercise testing 1

• Always perform exercise/treadmill ABI when iliac disease is suspected, as this unmasks hemodynamically significant proximal disease that appears normal at rest 1

Why Cross-Sectional Imaging is Superior

CT angiography should be the primary anatomic imaging modality for suspected iliac disease requiring revascularization because:

• Complete anatomic visualization from aorta through lower extremities in a single study 1

• Precise localization of disease and accurate assessment of stenosis severity for surgical planning 1

• Not affected by bowel gas, calcification, or operator variability that limit duplex ultrasound 3