If a thrombus is non-obstructive, how might Doppler signals appear?

• A. Can be normal
• B. Always obstructed
• C. Always reversed
• D. Never detectable

Answer: (A)

Non-obstructive means the vessel isn’t fully blocked, so there can still be passage of blood around or through the thrombus. Because Doppler ultrasound detects moving red blood cells, you can see normal Doppler signals even though a clot is present. The flow may be preserved enough to produce typical color fill and normal spectral waveforms, though in some cases flow can be reduced or dampened if the thrombus narrows the lumen. So it’s completely plausible to encounter normal Doppler signals in a non-obstructive thrombus.