A patient with intermittent claudication, decreased sensation and painful left leg while walking, relieved with rest, and absent distal pulses, what is the most appropriate initial investigation for suspected peripheral arterial disease (PAD)?

Vascular Ultrasound is the Most Appropriate Initial Investigation

For a patient with classic intermittent claudication and absent distal pulses bilaterally, vascular ultrasound (duplex Doppler) is the most appropriate initial investigation to confirm the diagnosis and localize disease before considering more advanced imaging for revascularization planning. 1

Clinical Context and Diagnostic Approach

This patient presents with textbook intermittent claudication—exertional leg pain relieved by rest—with bilateral absent distal pulses but preserved femoral and popliteal pulses, indicating infrainguinal (below-knee) arterial disease. 1

Why Vascular Ultrasound is the Best Initial Choice

• Duplex ultrasound is specifically recommended by the ACC/AHA as the first-line imaging method to confirm lower extremity arterial disease (LEAD) lesions after clinical suspicion is established. 1

• The ACR Appropriateness Criteria explicitly state that duplex US of the extremities can identify the location, degree, and extent of stenosis to the level of the knee with sensitivity and specificity of approximately 90-95% for stenoses >50%. 1

• Vascular ultrasound is non-invasive, widely available, does not require contrast or radiation exposure, and provides both anatomic and hemodynamic information through velocity measurements. 1

• This patient's clinical presentation (bilateral absent distal pulses with preserved proximal pulses) suggests multilevel infrainguinal disease that duplex ultrasound can effectively evaluate from the iliac arteries to the popliteal level. 1

When to Proceed to Advanced Imaging

• CT angiography or MR angiography should be reserved for patients in whom revascularization is being actively considered, not as initial diagnostic tests. 1

• The ACC/AHA guidelines explicitly state that duplex ultrasound, CTA, or MRA of the lower extremities is useful to diagnose anatomic location and severity of stenosis for patients with symptomatic PAD in whom revascularization is considered—meaning these are second-line tests after the diagnosis is confirmed. 1

• The ACR notes that while MRA with contrast (rated 8/9) and CTA with contrast (rated 8/9) provide excellent anatomic detail for revascularization planning, they are "usually appropriate" for assessment for revascularization, not initial diagnosis. 1, 2

Important Clinical Algorithm

Step 1: Confirm PAD diagnosis with ankle-brachial index (ABI) measurement—this should have already been done or should be done immediately alongside ultrasound. 1

Step 2: Perform duplex ultrasound to localize disease and assess severity. 1

Step 3: If the patient has significant functional impairment despite optimal medical therapy and supervised exercise, AND duplex ultrasound shows lesion anatomy amenable to revascularization, THEN proceed to CTA or MRA for detailed anatomic mapping. 1, 2

Step 4: Reserve conventional catheter angiography only for the time of planned intervention, not as a diagnostic test. 1, 2

Critical Pitfalls to Avoid

• Do not order CTA or MRA as the first test—this exposes the patient to unnecessary contrast (with renal toxicity risk) or radiation when the diagnosis can be confirmed non-invasively. 1

• Conventional angiography (Option C) is explicitly NOT appropriate as an initial investigation—the ACR states it "remains the reference standard" but should be pursued "only once an intervention is planned." 1, 3

• The presence of bilateral disease does NOT automatically warrant cross-sectional imaging—most patients with claudication are managed medically with risk factor modification, antiplatelet therapy, and supervised exercise therapy, making invasive imaging unnecessary initially. 1

Special Considerations

• Duplex ultrasound accuracy is diminished in the setting of multiple sequential lesions, dense calcification, or when evaluating tibial arteries for distal bypass planning—in these specific scenarios, CTA or MRA may be needed earlier. 1

• If duplex ultrasound shows disease amenable to revascularization AND the patient meets criteria for intervention (significant functional impairment, failed medical therapy, appropriate surgical risk), then proceed to CTA (preferred) or MRA for detailed anatomic planning. 2

• The ACC/AHA emphasizes that patients should receive comprehensive risk factor modification and antiplatelet therapy BEFORE any consideration of revascularization, making the urgency for advanced imaging lower in most claudication cases. 1