Sympathetic activity in the proximal urethra in patients with urinary obstruction

The effect of 10 mg. phentolamine intravenously on the urethral pressure profile was studied in male and female patients with lower urinary tract obstruction. A significant decrease of pressure occurred along the whole length of the urethra in both sexes, including the peak pressure zone in the male patient. This zone has been traditionally attributed to the external sphincter. It was concluded that the sympathetically innervated smooth muscle exerts a certain activity along the whole length of the proximal urethra. The phentolamine test may prove to be a useful adjunct to urethral profile studies in patients with lower urinary tract obstruction.