Prevalence and pattern of unstable urethral pressure in one hundred seventy-four gynecologic patients referred for urodynamic investigation.

Simultaneous urethrocystometry was performed in 174 gynecologic patients who complained of lower urinary tract symptoms. Thirty-five patients (20%) had a urethral pressure that fluctuated 20 cm H2O or more at two or more registrations. The degree of instability varied during urethrocystometry and from recording to recording in the same patient. No statistical difference was found between urethral pressure variation at 100 ml bladder volume, during bladder filling, or at bladder capacity. The prevalences of unstable urethral pressure in sensory urge incontinence and stress incontinence were 56% and 12%, respectively. The difference is highly significant. The prevalence of unstable urethral pressure in motor urge incontinence was 29%, and that in mixed incontinence was 22%. Three patients had unstable urethra, and six patients had unstable urethral pressure as the only sign. Thus, unstable urethral pressure can be considered to be a permanent sign that is recorded relatively often in patients with urinary incontinence. It may be an important part of the underlying mechanism in sensory urge incontinence and may, perhaps, be considered to be a clinical condition in itself.