In Doppler ultrasound, what does post-stenotic turbulence indicate?

• A. Turbulent flow distal to the narrowing indicating significant stenosis.
• B. Laminar flow throughout the vessel.
• C. Increased diastolic flow with no turbulence.
• D. No Doppler signal detected.

Answer: (A)

Post-stenotic turbulence signals that a narrowing is large enough to disrupt normal flow. When blood is squeezed through a narrowed segment, it speeds up to maintain the same flow rate. Once it exits into the wider vessel, that high-velocity jet blows into slower, nonuniform flow, creating swirling eddies and instability. On Doppler, this shows up as spectral broadening and a mosaic of colors distal to the narrowing. That chaotic, disturbed flow is a hallmark of hemodynamically significant stenosis because it reflects the jet becoming unstable as it transitions from the constricted region to the normal vessel.

If the flow remained laminar throughout, you wouldn’t see turbulence downstream. Increased diastolic flow without turbulence wouldn’t explain the disturbed distal pattern. No Doppler signal could occur for technical reasons or very low flow, not specifically indicating post-stenotic turbulence.