What combination of studies is typically performed in penile pressure and waveform testing?

• A. CT angiography of penis
• B. Duplex scan before and after injection with papaverine or prostaglandin; CW Doppler; 8-10 MHz; Plethysmography
• C. MRI of penis
• D. Duplex scan after exercise

Answer: (B)

Penile pressure and waveform testing relies on evaluating how well blood can flow into the penis and how effectively it is retained when erection is induced. The best way to do this is with a duplex ultrasound performed before and after injecting a vasodilator into the corpora cavernosa (such as papaverine or prostaglandin E1). This pharmacologic erection amplifies blood flow, revealing vascular issues that aren’t evident in the flaccid state.

Using a continuous-wave Doppler probe (typically with a high-frequency transducer around 8–10 MHz) allows precise measurement of flow velocities in the cavernosal arteries while color Doppler maps the vessels. Measuring both the baseline and post-injection states gives a dynamic picture of arterial inflow and helps identify venous leak by watching end-diastolic flow during sustained erection.

Plethysmography may be included to quantify changes in penile volume and further support assessment of venous outflow, enhancing the overall vascular evaluation.

Why this approach fits best: it combines functional testing (induced erection) with quantitative hemodynamics (flow velocities and spectral data) in real time, providing direct information about arterial inflow and venous competence. Other imaging modalities like CT angiography or MRI are anatomical and don’t reliably capture dynamic erectile physiology, and a duplex study after exercise misses the pharmacologically induced state needed to reveal functional patency and leakage.