The urethra is a reliable witness: simplifying the diagnosis of stress urinary incontinence

Abstract

In 1970, Bates, Whiteside, and Turner-Warwick [1] wrote that: “...the bladder often proves to be an unreliable witness...” and this phrase has been used for more than 40 years as a justification for urodynamic studies (UDS) in the evaluation of urinary incontinence. However, two studies published this year in the New England Journal of Medicine have reported the predictive value of direct observation of fluid loss from the urethra in making the diagnosis of stress urinary incontinence (SUI) [2] and occult SUI [3]. The studies suggest that for SUI or occult SUI, appropriate management decisions can be made with an office evaluation that includes demonstrating urine loss from the urethra without additional UDS. It probably should not surprise us that SUI is not a condition that requires urodynamic testing. SUI is a urethral problem and current bladder investigations do not investigate urethral conditions very well. Valsalva leak point pressures only indirectly measure urethral pressure, and urethral pressure profilometry typically only measures urethral function at rest and not during SUI conditions. No quantitative or qualitative measure during urodynamics makes the diagnosis of urodynamic stress incontinence (USI); thus, the diagnosis of USI is still dependent on direct visualization or imaging of fluid loss per urethra with cough or Valsalva. The presence of a catheter in the bladder (UDS) adds nothing of value to the diagnosis of SUI, except that it can confirm the absence of a cough or Valsalva provoked detrusor contraction. One could argue, though, that this type of detrusor event would not produce simultaneous fluid loss with cough, because a detrusor smooth muscle is not a striated muscle and cannot contract fast enough to generate detrusor pressure at the same time as a cough. Thus, there seems to be a limited role for urodynamics for SUI in the setting of a comprehensive history, office evaluation, and examination. Unfortunately, the current medical model encourages diagnostic studies whether or not they are necessary. This editorial proposes that the diagnosis of uncomplicated SUI and occult SUI by an office stress test and the management of it does not require urodynamic testing in most patients.