In pre-injection duplex imaging, which resistivity pattern is seen in the penile arteries?

• A. High-resistivity
• B. Low-resistivity
• C. Normal resistivity
• D. Inverted pattern

Answer: (A)

In baseline penile duplex ultrasound, you’re looking at the flaccid state of the penis. Here the cavernosal arterial bed offers higher resistance to flow because the tissue is not engorged and the downstream vascular bed is relatively constricted. On spectral Doppler this shows as a high-resistance waveform: a sharp systolic peak, an early diastolic notch, and limited diastolic flow. The resistive index will be relatively high in this state.

This is why the pre-injection pattern is described as high-resistivity. After a vasodilatory stimulus is given, the arteries dilate, resistance drops, and diastolic flow increases, producing a low-resistance waveform.