A 62-year-old man with diabetes and smoking history presents with claudication in the right lower limb for 3 months. On examination, the right femoral pulse is diminished and there is absence of dorsalis pedis pulse. What is the investigation of choice to confirm the diagnosis and determine the level of arterial stenosis?

Explanation

## Investigation of Choice in Peripheral Arterial Disease **Key Point:** Duplex ultrasonography is the first-line imaging modality for suspected peripheral arterial disease due to its non-invasive nature, lack of radiation, no contrast requirement, and excellent sensitivity for detecting stenosis and occlusion. ### Why Duplex Ultrasonography? 1. **Non-invasive and safe** — no radiation, no contrast, no nephrotoxicity risk 2. **High sensitivity and specificity** — 85–95% for detecting hemodynamically significant stenosis (>50%) 3. **Operator-dependent but reproducible** — can be repeated serially to monitor disease progression 4. **Cost-effective** — widely available in most centres 5. **Functional information** — provides both anatomical (B-mode) and hemodynamic (Doppler) data 6. **Real-time assessment** — allows dynamic evaluation of flow patterns ### Role of Other Investigations | Investigation | Role | When Used | |---|---|---| | **CT Angiography** | High sensitivity, excellent for calcification assessment, faster | When duplex inconclusive or contraindication to MRA; pre-intervention planning | | **MR Angiography** | No radiation, good for soft tissue, contraindicated in metallic implants | When CT contraindicated; renal insufficiency (non-contrast MRA) | | **Digital Subtraction Angiography** | Gold standard, invasive, reserved for therapeutic intervention | Therapeutic intervention (angioplasty, stent), not diagnostic | **Clinical Pearl:** Duplex ultrasonography is the recommended first-line investigation in all major guidelines (ACC/AHA, ESC) for initial assessment of PAD. It guides the need for further imaging and determines candidacy for intervention. **High-Yield:** The ankle-brachial index (ABI) measured during duplex or as a standalone test (ABI <0.9 = PAD) is the simplest screening tool, but duplex provides anatomical localization of stenosis. **Tip:** Remember the investigation hierarchy: clinical examination → ABI/duplex → CT/MR angiography → angiography (only for intervention).