Unstable urethral pressure: Toward a more relevant definition

Abstract There is confusion in the literature over the use of the terms unstable urethra and unstable urethral pressure , which are often held inappropriately to be synonymous. The importance of the former condition, as a cause of incontinence, is beyond doubt, although it appears to be an uncommon condition; the finding of unstable urethral pressure is reported much more frequently, although its clinical significance remains in debate. An analysis of urethral pressure recordings in a group of 131 women with urodynamically proven genuine stress incontinence, and 14 urodynamically normal women entirely free from urinary symptoms has been carried out in an attempt to define the differences between the two and thus to establish a more clinically relevant definition for the phenomenon of “unstable urethral pressure.” The variation in urethral pressure was calculated first in absolute terms, as the variation in cm H 2 O above and below the mean maximum urethral closure pressure (MUCP), and second in relative terms, as a percentage of the mean MUCP itself; these two parameters are described as “ delta‐MUCP ( absolute )” and “ delta‐MUCP ( relative ),” respectively. The mean delta‐MUCP (absolute) values were 9.5 and 13.4 cm H 2 O for the symptomatic and control groups, respectively (not significant); the mean delta‐MUCP (relative) values were 27.0% and 17.1% of the MUCP (p < 0.001). Examination of various potential points of discrimination for the diagnosis of “unstable urethral pressure” showed a delta‐MUCP (relative) of 30% to be the best discriminator, allowing the identification of a subgroup of stress incontinent women whose urethral pressure variation was likely to be of relevance in the determination of symptoms.