Pelvic Floor Stress Response: Reflex Contraction with Pressure Transmission to the Urethra

Abstract

There is still controversy regarding the active role of striated intramural and periurethral muscles and their relative share of function for urinary continence under stress conditions. To evaluate the function of the periurethral muscles, we subjected a dog model to the physiologic stress condition created by sneezing. Simultaneous measurements of intravesical and three urethral pressures were obtained in the intact urinary tract and in a noncontractile substitute urethra, which was pulled through the pelvic floor and studied with and without additional pelvic floor suspension. The data clearly confirm the active role of striated sphincteric muscles for continence under stress conditions. The reflex contraction of the striated sphincteric muscles constitutes the majority of the distal urethral closure mechanism under stress conditions and generates intraurethral pressures, which exceed those of passive transmission of intra-abdominal pressure. The intramural striated sphincter contributes a share of less than 10% to this stress response, while the vast majority of the pressure rise is generated by the periurethral striated muscles. Surgical suspension of the pelvic floor can enhance effectivity of this stress mechanism, and thus seems to be a sound physiological concept in surgical treatment of incontinence.

Effect of Duloxetine on Urethral Resting Pressure and on Sphincter Contractility in Response to Coughing and Magnetic Stimulation in Healthy Women

“…During coughing, continence mechanisms include both passive and active closure of the urethra . A passive closure mechanism is characterized by the simultaneous transmission of abdominal pressure to the urinary bladder and proximal urethra.…”

The pelvic floor muscles: Muscle thickness in healthy and urinary-incontinent women measured by perineal ultrasonography with reference to the effect of pelvic floor training. Estrogen receptor studies

“…The adjunctive closure mechanisms are partly composed of a passive pressure transmission to the bladder neck and proximal urethra during intraabdominal pressure rise and partly by active pressure transmission during voluntary contraction of the intra-and periurethral striated muscles, i.e., the urethral sphincter (the rhabdosphinc-ter), the compressor urethra, the urethrovaginal sphincter, and the pelvic floor muscles [Enhörning, 1961;Constantinou and Govan, 1982;Thüroff et al, 1982Thüroff et al, , 1987Massey et al, 1987;Heidler et al, 1987;Tanagho et al, 1969a;Lose and Colstrup, 1991;Thind and Lose, 1992].…”

Urethral pressure response to cough and voluntary perineal contraction in men without previous pelvic surgery

“…An animal model using dogs showed that the urethral sphincter as well as perineal muscles induced urethral pressure increase in response to cough [Thuroff et al, 1992[Thuroff et al, , 1987. The urethral pressure variations with cough and voluntary perineal contraction were extensively described in women to explore stress incontinence.…”