Lower Extremity Arterial Duplex

1. 1

   Record bilateral ankle-brachial index (ABI) before scanning. Patient supine. Use linear probe (5–12 MHz); curved probe for proximal iliacs.

2. 2

   Begin at CFA in groin: transverse survey for plaque, then longitudinal Doppler. Note waveform character — triphasic is normal in a resting limb.

3. 3

   Follow SFA from groin to adductor canal: scan in transverse to identify stenosis or occlusion, then sample Doppler every 5–10 cm. Calculate PSV ratio at any focal acceleration (>2.0 = ≥50% stenosis).

4. 4

   Popliteal artery: probe posteriorly or medially with knee slightly flexed. Sample Doppler proximal, mid, and distal popliteal.

5. 5

   Tibioperoneal trunk: identify bifurcation below popliteal fossa. Follow posterior tibial (medial) and peroneal arteries.

6. 6

   Anterior tibial artery: begins at bifurcation, courses anterolaterally through interosseous membrane. Follow to dorsalis pedis at dorsum of foot.

7. 7

   Document each segment as: normal triphasic, biphasic (mild-moderate disease), monophasic (severe inflow disease), or absent (occlusion). Note collateral vessels bridging occlusions.

• Aortoiliac segment — Doppler
• Common femoral artery (CFA) — Doppler
• Superficial femoral artery (SFA) — proximal, mid, distal
• Popliteal artery — Doppler
• Tibioperoneal trunk + anterior tibial artery
• Posterior tibial artery — Doppler
• Peroneal artery — Doppler
• Dorsalis pedis artery — Doppler

• Waveform character (triphasic/biphasic/monophasic)
• PSV and PSV ratio at each segment
• Plaque burden and calcification
• Stenosis location and severity
• Collateral vessel development

• Highly calcified vessels (Mönckeberg sclerosis) may be non-compressible — do not confuse with occlusion
• A PSV ratio >2.0 indicates ≥50% stenosis; >4.0 indicates >70% stenosis
• Monophasic waveform distally may reflect inflow disease rather than local disease
• Heavy calcification causes acoustic shadowing — rely on Doppler alone at those segments

Document ABI before the exam. An ABI <0.9 confirms PAD; <0.4 indicates critical limb ischemia. Triphasic → biphasic → monophasic waveform progression indicates increasing proximal inflow disease.