Figure 2. (a) Spectral Doppler ultrasound, at 15 min following 20 µg prostaglandin E1, demonstrates an excellent arterial response (peak systolic velocity=77.1 cm s^–1) but a high forward diastolic flow of 16.7 cm s^–1, suggesting the presence of a venous leak. (b) Following the administration of 2 mg intracavernosal phentolamine, there is no change of the spectral Doppler ultrasound waveform, with a slight rise in the peak systolic velocity to 89.4 cm s^–1. There is little change in the end diastolic velocity (17.5 cm s^–1), suggesting the presence of a "true" venous leak.