Urethral retro-resistance pressure: a new clinical measure of urethral function

The urethral retro-resistance pressure (URP) is a new retrograde measurement of urethral function. URP is the pressure required to achieve and maintain an open sphincter. The assessment of any potential diagnostic measure must include an evaluation in individuals both with and without disease. In this study, we examined URP values in women without urinary incontinence.

Four centers enrolled 61 women who did not report symptoms of urinary incontinence, and who had negative standing stress tests (SST). Each center was to perform three consecutive URP measurements on each subject. At two centers, 32 subjects returned in 3-7 days for three additional URP measurements. We compared the average URP in this asymptomatic population to the average URP from women symptomatic of stress urinary incontinence (SUI) derived from a previous study. We evaluated the within-subject variation of the URP measurement at a single visit and the within-subject change in URP over time using test and retest values.

The mean age was 33 +/- 9 years and the mean body mass index (BMI) was 24 +/- 6. URP values were normally distributed. The mean URP at visit 1 was 112.6 +/- 39.2 cm H2O (n = 60). This was statistically significantly different from the mean URP of symptomatic women (69.9 cm H2O, P < 0.0001). The within-subject standard deviation of URP at visit 1 was 12.6 +/- 12.6 cm H2O (n = 60) and at retest visit was 9.3 +/- 6.2 cm H2O (n = 32). For the retest cases, the mean URP at visit 1 was 113.9 +/- 39.9 cm H2O (n = 32) and at retest visit was 125.5 +/- 33.9 cm H2O (n = 32) (Wilcoxon Signed Rank test, P = 0.145).

The mean URP measurement obtained in this study of asymptomatic women showed significantly higher values when compared to our study in women with SUI. The URP measurements were consistent within the same subject. Furthermore, there was no statistically significant difference in the URP measurement from visit 1 to retest visit. The data suggest that URP shows promise as a physiological urethral pressure measurement.