How Does the Urethra Respond to Bladder Filling in Continent and Incontinent Women?

Abstract

The objective of this study was to describe mean urethral pressure (MUP) during filling cystometry in continent and incontinent women. Incontinent women were recruited from a urogynecology clinic if they answered "sometimes" or "always" to 1 of the items on the Medical, Epidemiologic, and Social Aspects of Aging questionnaire. Participants were categorized by Medical, Epidemiologic, and Social Aspects of Aging scores into stress urinary incontinence (SUI) or urgency urinary incontinence (UUI) groups. Continent women were recruited from the community. Multichannel urodynamics were performed using microtip catheters. Urethral pressure profiles were obtained with an empty bladder and at 100-mL increments during filling. Data were analyzed in SPSS. Continuous variables were compared with independent t test or analysis of variance, categorical variables with the χ2 test, and multivariable comparisons were made with linear regression. Eighty-six women (30 continent, 56 incontinent: 37 SUI, 19 UUI) with a mean ± SD age of 48 ± 15 years and a body mass index (BMI) of 31 ± 9 participated. Sixty-nine percent were White, 43% were postmenopausal, and 80% were parous. Continent women were younger (P < 0.001) and had a lower BMI (P = 0.004). Mean cystometric capacity was higher in women with SUI and continent women than in women with UUI (430 ± 142, 448 ± 101, and 332 ± 160, P = 0.04). Continent women had higher MUP at baseline when controlling for age, BMI, and parity (84 ± 35 cmH2O vs 62 ± 28 cmH2O; aR2 = 0.2, P = 0.02) compared with incontinent women. During filling, MUP in continent women was 20-30 cmH2O higher at all bladder volumes than incontinent women. Mean urethral pressure increased significantly between baseline and 300 mL in continent women (P < 0.005) and women with SUI (P = 0.04), but not in women with UUI (P = 0.48). Continent women have greater baseline MUP and greater increases in MUP during bladder filling than incontinent women.