Effect of vaginal distention on vesicourethral function with identification of the vagino-vesicourethral reflex

Purpose: To our knowledge the physiological mechanisms involved in sexual i ntercourse have not been completely explored. We hypothesized that vaginal distention induced by penile thrusting may affect the function of the bladd er and urethra. To verify this supposition we assessed the effect of vagina l distention on vesical and urethral pressure. No relevant reports in the l iterature were identified. Materials and Methods: The response of vesical and urethral pressure to vag inal distention was recorded in 26 healthy women volunteers with a mean age plus or minus standard deviation of 36.7 +/- 9.8 years. A condom was intro duced into the vagina and inflated with carbon dioxide in increments of 10 mi. up to 80 ml. Vesical and urethral pressure was measured by a 2-channel microtip catheter connected to a transducer. The vesicourethral pressure re sponse to vaginal distention was also tested after individual anesthetizati on of the bladder, urethra and vagina. Results: No vesicourethral pressure response was recorded with 10 and 20 mi . of vaginal distention. At 30 and up to 80 mi. of distention bladder press ure decreased and urethral pressure increased (p <0.05). There was no signi ficant difference when the volume of vaginal distention was increased. Mean duration of the pressure response was 4.2 +/- 0.6 seconds. Pressure return ed to normal after a latency period of 5.2 +/- 1.1 seconds, although the va gina was continuously distended. Vaginal distention during anesthetization of the bladder, urethra or vagina did not evoke a pressure response. Conclusions: The vesicourethral response to the inserted condom, which by i nflation adopts the shape of the erect penis, seems to simulate the respons e of the vagina when it is distended by the erect penis during coitus. The constant vesicourethral pressure response to vaginal distention postulates a reflex relation, which we call the vagino-vesicourethral reflex. This ref lex is apparently evoked during coitus, leading to momentary vesical dilata tion and increased urethral sphincter activity, which most Likely acts to p revent urinary leakage during coitus. Reflex disorders may explain urinary leakage during coitus in some neuropathic conditions.