Effect of perineal compression on vesical motor activity.

Objective: It has been reported that digital pressure on the perineum inhibits bladder contraction; however, the mechanism is not fully understood. We investigated the hypothesis that this mechanism may be reflex in nature. Material and Methods: A total of 21 healthy volunteers (13 males; mean age 42.3 +/- 11.8 years) were studied. A barostat system consisting of a balloon-ended catheter connected to a strain gauge and air-injection system was used to assess vesical tone. The catheter was introduced into the urinary bladder and the balloon was inflated with 150 ml of air. Digital pressure was exerted on the perineum and the vesical tone was simultaneously assessed by recording the balloon volume variations, expressed as the percentage change from the baseline volume. The test was repeated after separate anesthetization of the perineum and bladder with xylocaine and after using normal saline instead of xylocaine. Results: Digital pressure on the perineum effected a significant decrease in vesical tone, which ranged from 42% to 84% (mean 67.5% +/- 12.5%) of the baseline value. The mean latency was 18.6 +/- 2.6 ms. There was no significant difference between men and women in terms of vesical tone response to perineal pressure. Digital perineal pressure applied 20 min after individual anesthetization of the perineum and bladder produced no significant changes in vesical tone. The response returned after the anesthetic effect had waned. The vesical tone response following saline administration was similar to that before administration. Conclusions: Vesical tone decrease in response to digital pressure on the perineum suggests a reflex relationship which was absent on individual anesthetization of the two possible arms of the reflex arc: the perineal skin and urinary bladder. We call this relationship the "perineovesical reflex". This reflex may have the potential to be used as an investigative tool in the diagnosis of vesical motor disorders.