Analysis of Continence Reflexes by Dynamic Urethral Pressure Recordings in a Rat Stress Urinary Incontinence Model Induced by Multiple Simulated Birth Traumas

The present study evaluated real-time changes in urethral pressure during the storage phase using a rat model with stress urinary incontinence (SUI) induced by simulated multiple birth traumas and investigated the relationship between urethral continence function and dynamic parameters associated with the changes in urethral pressure. Sprague-Dawley rats were divided into the following two groups: the sham group, which underwent three catheterizations of the vagina without distension at 2-wk intervals, and the vaginal distension (VD) group, which underwent three VDs at 2-wk intervals. After transection of the T8-T9 spinal cord, simultaneous bladder and urethral pressure recordings were performed during intravesical pressure elevation. Urodynamic parameters such as leak point pressure (LPP), urethral baseline pressure (UBP), maximum urethral pressure (MUP), the MUP-UBP differential (dUP) during intravesical pressure elevation, the bladder pressure when urethral contraction begins (Puc), and the bladder pressure at bladder neck opening (Pno) were then measured and compared. Compared with the sham group, LPP, UBP, dUP, MUP, Puc, and Pno were significantly decreased in the VD group. Pressure differences between LPP and Pno and between LPP and UBP (LPP-UBP) were also significantly different in the two groups. However, difference values of LPP and MUP or Pno and UBP were not altered after VD. Our new methods of simultaneous recordings of dynamic changes in bladder and urethral pressures are useful to fully evaluate the functional alterations in urethral continence function in the SUI model induced by multiple VDs. Moreover, LPP-UBP values, which correspond to the difference between Valsalva LPP and maximum urethral closure pressure in clinical urodynamics, would be useful to evaluate the impaired urethral continence function after simulated birth traumas in animal models.