Objective: To assess dynamic intraurethral sonography in the diagnostic evaluation of the function of the rhabdosphincter in female patients with urinary stress incontinence in relation to patient age.
Methods: Sixty-two patients with clinically proved urinary stress incontinence were investigated by means of intraurethral sonography with a 12.5-MHz endoluminal 9F catheter. The omega-shaped rhabdosphincter was visualized at rest and during voluntary contractions. Changes of muscle thickness and transducer-sphincter distance were measured and considered as parameters of muscle function. The intraurethral sonographic data were compared with results of standard urodynamic tests.
Results: Transducer-sphincter distance and sphincter muscle thickness showed a significant decrease with positive linear dependency on patient age (P < .001). Patients with grade III urinary stress incontinence had complete loss of sphincter contractility. A negative correlation was revealed between urethral closure pressure and patient age.
Conclusions: We found an age-related decrease in rhabdosphincter function. Our results suggest that the rhabdosphincter is a substantial component of the continence mechanism in female urinary stress incontinence. Unlike urethral pressure profiles, which can only reveal zones of higher intraluminal pressure, transurethral sonography is highly specific for measurement of the function of the rhabdosphincter.