With vascular calcifications seen on an ankle X‑ray, should I order a comprehensive duplex ultrasound of both lower limbs (including femoral and iliac arteries) or only a distal lower‑leg ultrasound?

Order a Comprehensive Lower Extremity Arterial Duplex Ultrasound (Including Iliac Arteries)

When vascular calcifications are incidentally found on ankle X-ray, you should order a complete duplex ultrasound of both lower extremities that includes evaluation from the iliac arteries down to the ankle—not just a distal lower-leg study.

Rationale for Comprehensive Imaging

Vascular calcifications on ankle X-ray are a marker of systemic atherosclerotic disease, and peripheral arterial disease (PAD) is rarely isolated to a single arterial segment. The disease typically involves multiple levels of the arterial tree, and duplex ultrasound from the iliac arteries to the popliteal arteries has 90-95% sensitivity and specificity for detecting significant stenoses 1.

Why Include Iliac Arteries?

• Iliac disease can be clinically silent at rest: Patients with isolated aortoiliac disease may have normal ankle-brachial indices (ABIs) at rest, making proximal disease easy to miss if you only image distally 2
• Duplex ultrasound performs well in the iliac segment: Studies demonstrate 92% sensitivity and 96% specificity for detecting significant aortoiliac lesions, with a kappa index of 0.81 showing good agreement with angiography 2
• Treatment planning requires knowing the full extent of disease: Whether the patient ultimately needs revascularization or medical management, understanding the complete anatomic distribution of atherosclerosis is essential 3, 4

The Standard Approach

The most recent ACC/AHA guidelines (2024) recommend duplex ultrasound, CTA, or MRA for assessment of anatomy and disease severity when evaluating PAD 3. Duplex ultrasound is the preferred initial imaging modality because it:

• Is non-invasive and radiation-free
• Requires no contrast (important if renal function is compromised)
• Provides both anatomic and hemodynamic information
• Can evaluate from iliac arteries through tibial vessels 1, 4

Practical Ordering Strategy

Order: "Bilateral lower extremity arterial duplex ultrasound with evaluation of iliac, femoral, popliteal, and tibial arteries"

This comprehensive study should include:

• Common and external iliac arteries bilaterally
• Common femoral arteries
• Superficial femoral arteries
• Popliteal arteries
• Tibial vessels (anterior tibial, posterior tibial, peroneal)

Important Caveats

Duplex ultrasound has limitations in the iliac segment that you should be aware of:

• Bowel gas can obscure iliac vessels 1
• Dense calcification (which your patient clearly has) can obscure flow, particularly if flow is slow 1
• The examination is operator-dependent and requires skilled sonographers 1

If the duplex study is technically limited in the iliac segment or shows abnormal spectral Doppler waveforms suggesting proximal disease that cannot be adequately visualized, you should have a low threshold to proceed with CTA or MRA for complete evaluation 5.

When to Consider Alternative Imaging

Consider CTA with runoff as your initial study instead of duplex if:

• The patient has symptoms suggesting multilevel disease requiring revascularization planning
• Duplex ultrasound quality is known to be limited at your institution
• The patient has chronic kidney disease with non-compressible vessels (making ABI unreliable) but adequate renal function for contrast

Do not order imaging of just the distal lower legs—this fragmented approach will miss proximal disease and likely require additional studies, increasing cost and delaying diagnosis 1.