Figure 1. (a) Following an intracavernosal injection of prostaglandin E1, at 15 min the peak systolic velocity of the right cavernosal artery measures 55.4 cm s^–1 and the end diastolic velocity remains above the baseline, measuring 2.4 cm s^–1. The degree of tumescence is suboptimal. (b) Following intracavernosal phentolamine (2 mg), the peak systolic velocity increases to 75.7 cm s^–1, but the end diastolic velocity demonstrates flow reversal (measured at –5.4 cm s^–1). This corresponds to a good degree of tumescence suggesting that the apparent leak in this patient was not structurally based but could be functional.