Influence of Pelvic Floor Muscle Contraction on the Profile of Vaginal Closure Pressure in Continent and Stress Urinary Incontinent Women

Abstract

We characterized the vaginal pressure profile as a representation of closure forces along the length and circumference of the vaginal wall. Vaginal pressure profile data were used to test the hypothesis that the strength of pelvic floor muscle contractions differs significantly between continent women and women with stress urinary incontinence. Vaginal pressure profile recordings were made in 23 continent subjects and in 10 patients with stress urinary incontinence. The recordings characterized closure forces along the entire length of the vagina and identified differences among the anterior, posterior, left and right sides of the vaginal wall. Using a novel, directionally sensitive vaginal probe we made vaginal pressure profile measurements with the women at rest and during pelvic floor muscle contraction while supine. The nature of the vaginal pressure profile was characterized in terms of force distribution in the anterior and posterior vaginal walls, which was significantly greater than that on the left and right sides. The continent group had significant greater maximum pressure than the stress urinary incontinence group on the posterior side at rest (mean +/- SE 3.4 +/- 0.3 vs 2.01 +/- 0.36 N/cm(2)) and during pelvic floor muscle contraction (4.18 +/- 0.26 vs 2.25 +/- 0.41 N/cm(2)). The activity pressure difference between the posterior and anterior vaginal walls in the continent group was significantly increased when the pelvic floor muscles contracted vs that at rest (3.29 +/- 0.21 vs 2.45 +/- 0.26 N/cm(2)). However, the change observed in the stress urinary incontinence group was not significant (1.85 +/- 0.38 vs 1.35 +/- 0.27 N/cm(2)). The results demonstrate that the voluntary pelvic floor muscles impose significant closure forces along the vaginal wall of continent women but not in women with stress urinary incontinence. The implication of these findings is that extrinsic urethral closure pressure is insufficiently augmented by pelvic floor muscle contraction in women with stress urinary incontinence.