Functional analysis of active urethral closure mechanisms under sneeze induced stress condition in a rat model of birth trauma

Purpose: We evaluated changes in the urethral closure mechanism under a sneeze induced stress condition in a rat model of birth trauma. Materials and Methods: Four days after vaginal distention induced by balloon catheter inflation in the vagina sneezing was induced while recording intravesical pressure with the rat under urethane anesthesia to evaluate sneeze induced leak point pressure, defined as the lowest pressure inducing fluid leakage from the urethral meatus during sneezing. Sneeze induced responses in the bladder and proximal or mid urethra were also measured using microtip transducer catheters. Results: In 5 sham operated rats no leakage was observed from the urethral meatus during sneezing, which produced an increase in intravesical pressure of up to 34 cm H2O. However, in 5 of 6 rats with vaginal distention leakage during sneezing was observed with a sneeze leak point pressure of 26.2 cm H2O. In the mid urethra microtip transducer catheters revealed that pressure increases during sneezing were greater than those in the bladder but they were significantly decreased in the 5 incontinent vaginal distention rats. However, sneeze induced responses at the proximal urethra, which were similar to those in the bladder, were not different in sham operated and incontinent vaginal distention rats. Conclusions: Sneeze induced stress urinary incontinence in a rat model of birth trauma was caused by decreased active closure mechanisms at the mid urethra without affecting the passive transmission of abdominal pressure in the proximal urethra.