Urodynamic analysis of urethral, vesical and perivesical pressure distribution in the healthy female.

The transmission of intra-abdominal pressures to the urethra of the healthy female is examined with respect to cough, Valsalva and holding stimuli. A new method of recording urethral pressures using a four-channel, perfused gap catheter specifically constructed for this investigation is used. The results show that the increase of urethral pressure to stimuli is magnified at the distal urethra to a significant degree. This magnification is significantly higher than that expected by direct intra-abdominal transmission. Anatomically, the focus of urethral magnification of pressures is located 2-3 mm distal to the external urethral sphincter. The data provided from this study indicate that the mechanism of action of urethral closure to stress is active and does not directly correspond to the transmission properties of the lower urinary tract to stresses. Evidence supporting this mechanism is drawn also from the differential behavior of the proximal and distal regions of the urethra to the initiation and cessation of voiding.