Objective: To compare the structure and function of the urethral sphincter and the urethral support in nulliparous black and white women. Methods: Eighteen black women (mean age 28.1 years) and 17 white women (mean age 31.3 years) completed this cross-sectional study. The following assessments were made: urethral function using multichannel cystometrics and urethral pressure profilometry, pelvic muscle strength using an instrumented speculum, urethral mobility using the cotton-swab test and perineal ultrasound, and pelvic muscle bulk using magnetic resonance imaging. Results: Black women demonstrated a 29% higher average urethral closure pressure during a maximum pelvic muscle contraction (154 cm H2O versus 119 cm H2O in the white subjects; P = .008). Although not statistically significant, black women had a 14% higher maximum urethral closure pressure at rest (108 cm H2O versus 95 cm H2O; P = .23) and a 21% larger urethral volume (4818 mm3 versus 3977 mm3; P = .06). In addition, there was a 36% greater vesical neck mobility measured with the cotton-swab test (blacks 49°versus whites 36°; P = .02) and a 42% difference in ultrasonically measured vesical neck mobility during a maximum Valsalva effort (blacks = -17 mm versus whites -12 mm; P = .08). Conclusion: Functional and morphologic differences exist in the urethral sphincteric and support system of nulliparous black and white women. Copyright (C) 2000 The American College of Obstetricians and Gynecologists.
Howard, D., Delancey, J. O. L., Tunn, R., & Ashton-Miller, J. A. (2000). Racial differences in the structure and function of the stress urinary continence mechanism. Obstetrics and Gynecology, 95(5), 713–717. https://doi.org/10.1016/S0029-7844(00)00786-9