Post-radical prostatectomy penile blood flow: assessment with color flow Doppler ultrasound

Cadaveric dissections have revealed that accessory blood vessels to the penis often arise near or through the apex of the prostate. These accessory vessels may be easily injured during radical prostatectomy. Increasing attention since the 1980s has focused on preserving potency after radical prostatectomy with a nerve sparing technique. However, many patients are impotent even after a nerve sparing procedure. An arterial, venous or psychological mechanism may be involved. A prospective study was designed to assess cavernous artery diameter, peak systolic flow velocity, penile blood flow, end diastolic flow velocity and resistance index preoperatively and postoperatively in patients undergoing radical prostatectomy. Ten patients with a mean age of 60 years were evaluated, of whom 8 underwent a unilateral nerve sparing procedure, 1 bilateral nerve sparing procedure and 1 bilateral nonnerve sparing procedure. Mean penile blood flow as calculated by the formula penile blood flow = peak systolic flow velocity x pi (diameter/2)2 increased 0.33 ml. per second (+26%) on the nerve spared side, while diminishing 0.68 ml. per second (-41%) on the nonspared side. Overall penile blood flow was diminished. End diastolic flow velocity increased on spared and nonspared sides after surgery. The resistance index for all radical prostatectomy patients diminished 7% from 0.83 preoperatively to 0.77 postoperatively (p = 0.16). While these findings were not statistically significant, they suggest that arterial insufficiency and corporeal venous occlusive dysfunction may be involved in sexual dysfunction after nerve sparing radical prostatectomy.