Change of external urethral sphincter function in prostatic patients.

External urethral function was urodynamically examined in 13 patients with benign prostatic hypertrophy (BPH) associated with chronic urinary retention and in 5 volunteers. Prevoiding drop in external urethral sphincter pressure was noted in all the volunteers, whereas it was not found in 6 of the 13 cases of BPH. Bladder neck opening pressure was higher in these 6 cases (p less than 0.05). After administration of phentolamine, prevoiding drop was noted in 5 of these 6 cases, and bladder neck opening pressure decreased so much that there was no significant intergroup difference. The above results mean that the increase in alpha-adrenergic receptors makes the prostate, which has been already hypertrophied, less elastic, inhibiting external urinary sphincter function.