What testing is sensitive and specific to diagnose the cause of a patient's right lower extremity (RLE) weakness with diminished pulses, also known as intermittent claudication or peripheral arterial disease (PAD)?

From the Guidelines

For a patient presenting to the ER with right lower extremity swelling and diminished pulses, duplex ultrasound is the recommended first-line diagnostic test. This non-invasive imaging modality combines B-mode ultrasound with Doppler flow studies and is both highly sensitive and specific for detecting vascular abnormalities, as supported by the 2024 ACC/AHA/AACVPR/APMA/ABC/SCAI/SVM/SVN/SVS/SIR/VESS guideline for the management of lower extremity peripheral artery disease 1. The test can quickly determine whether the patient has deep vein thrombosis, arterial occlusion, or another vascular condition causing the symptoms.

Key Considerations

• Duplex ultrasound allows visualization of blood vessels and assessment of blood flow in real-time, helping to distinguish between arterial and venous pathologies.
• If arterial insufficiency is suspected based on the diminished pulses, the ankle-brachial index (ABI) should also be performed, which compares blood pressure in the ankle to that in the arm, as discussed in the guidelines for the acute care of severe limb trauma patients 1.
• For cases where ultrasound results are inconclusive or if more detailed anatomical information is needed, CT angiography or MR angiography may be warranted as second-line tests, as recommended in the 2024 ACC/AHA/AACVPR/APMA/ABC/SCAI/SVM/SVN/SVS/SIR/VESS guideline 1.
• These imaging studies provide comprehensive vascular mapping but require contrast administration and are more resource-intensive than ultrasound.

Diagnostic Approach

• The choice of imaging modality is individualized based on patient and imaging modality-based factors as well as local availability of resources, as noted in the 2024 guideline 1.
• Noninvasive cross-sectional imaging (ie, duplex ultrasound, CTA, or MRA) is often obtained in planning revascularization, and validation studies comparing these modalities with catheter angiography have included patients with CLTI, as discussed in the guideline 1.
• For some patients with CLTI, proceeding directly to invasive catheter angiography followed by endovascular revascularization during the same session avoids delay and can minimize potential risks associated with prerevascularization noninvasive imaging, as suggested in the guideline 1.

From the Research

Diagnostic Testing for Lower Extremity Arterial Disease

To determine the diagnosis of a patient presenting with validation of right lower extremity with diminished pulses, several diagnostic tests can be used. The following are some of the testing options that are sensitive and specific for diagnosing lower extremity arterial disease:

• Duplex ultrasonography: This test has a sensitivity of 88% (range 80-98%) and a specificity of 96% (range 89-99%) for detecting stenosis of 50% or more in a lower limb vessel 2.
• Computed Tomography Angiography (CTA): CTA has a sensitivity of 91% (range 89-99%) and a specificity of 91% (range 83-97%) for detecting stenosis of 50% or more in a lower limb vessel 2.
• Magnetic Resonance Angiography (MRA): MRA has a sensitivity of 95% (range 92-99.5%) and a specificity of 97% (range 64-99%) for detecting stenosis of 50% or more in a lower limb vessel 2.
• Contrast-enhanced MRA: This test has been shown to be more specific than CTA and more sensitive than duplex ultrasonography for detecting stenosis of 50% or more in a lower limb vessel 2.

Comparison of Diagnostic Tests

The choice of diagnostic test depends on various factors, including the patient's symptoms, medical history, and the availability of testing facilities. The following are some of the advantages and disadvantages of each test:

• Duplex ultrasonography: Advantages - non-invasive, low cost, and widely available; Disadvantages - operator-dependent, may not be accurate for detecting stenosis in certain areas of the lower extremity 2.
• CTA: Advantages - high sensitivity and specificity, can detect stenosis in multiple areas of the lower extremity; Disadvantages - requires contrast agent, may not be suitable for patients with kidney disease or allergy to contrast agent 2.
• MRA: Advantages - high sensitivity and specificity, can detect stenosis in multiple areas of the lower extremity; Disadvantages - may not be suitable for patients with claustrophobia or certain metal implants, requires contrast agent 2.

Clinical Application

The diagnostic tests mentioned above can be used in various clinical settings, including:

• Diagnosis of lower extremity arterial disease: These tests can help diagnose stenosis or occlusion of the lower extremity arteries, which can cause symptoms such as claudication, pain, or numbness in the legs.
• Preoperative evaluation: These tests can be used to evaluate the extent of disease and plan surgical or endovascular interventions.
• Monitoring of disease progression: These tests can be used to monitor the progression of disease and adjust treatment plans accordingly.