Carotid Ultrasound: Purpose, Procedure, and What It Detects

A carotid ultrasound (carotid duplex scan) is a non-invasive, radiation-free imaging test that evaluates the carotid arteries in the neck—the main blood vessels supplying the brain.

Why It’s Ordered

• Screen for carotid artery stenosis (narrowing) due to atherosclerosis, a major risk factor for ischemic stroke.
• Evaluate transient ischemic attack (TIA) or stroke symptoms.
• Assess carotid plaque characteristics (calcified vs. soft/vulnerable).
• Detect dissection, aneurysm, or hematoma after trauma.
• Monitor post-operative status after carotid endarterectomy or stenting.
• Screen asymptomatic patients with multiple vascular risk factors (e.g., diabetes, smoking, coronary artery disease).

What the Exam Shows

• B-mode imaging: Vessel wall thickness (intima-media thickness), plaque presence, morphology, and ulceration.
• Doppler spectral analysis: Blood flow velocity, direction, and turbulence—used to grade stenosis (e.g., NASCET criteria).
• Color Doppler: Visual map of flow patterns and collateral circulation.

Procedure and Preparation

• No fasting or sedation required.
• Patient lies supine with neck slightly extended and turned away from the side being examined.
• Water-based gel applied; transducer moved along the neck from clavicle to jaw angle.
• Typically takes 15–30 minutes; painless.

Interpretation and Next Steps

• Normal: No plaque, normal velocities (PSV <125 cm/s).
• <50% stenosis: Medical management (statins, antiplatelets, risk factor control); repeat imaging per guidelines.
• 50–69% stenosis (symptomatic): Consider carotid endarterectomy or stenting.
• ≥70% stenosis: Strong consideration for revascularization if symptomatic; individualized if asymptomatic.
• Near-occlusion/occlusion: High stroke risk; medical management paramount.

Carotid ultrasound is a first-line, cost-effective tool for stroke risk stratification. It does not image intracranial vessels; CT/MR angiography may be needed for complete cerebrovascular assessment.