Clinical assessment of urethral sphincter function.

Measurements of urethral pressures, such as maximum urethral pressure, are widely believed to have relevance in the management of urinary incontinence despite evidence to the contrary. In this study maximum urethral pressure and the abdominal pressure required to cause stress incontinence were measured in 125 women with stress incontinence. In women the abdominal pressure required to cause stress incontinence was unrelated to maximum urethral pressure. These findings indicate that maximum urethral pressure has little relationship to urethral resistance to abdominal pressure. In the 9 children with myelodysplasia we compared the detrusor pressure with the abdominal pressure required to induce urethral leakage. These values also were quite different, indicating that as far as the urethra is concerned abdominal pressure and detrusor pressure are not equivalent forces.