Racial differences in female urethral morphology and levator hiatal dimensions: an ultrasound study

To compare the urethral sphincter morphology and levator hiatal dimensions between white and black premenopausal nulliparous asymptomatic women using 3D/4D translabial ultrasonography.

Nulliparous black and white women were recruited in a tertiary gynecological center. All women were completely asymptomatic for pelvic floor dysfunction. Women were assessed with 3D/4D translabial ultrasound scan of the pelvic floor, at rest. Measurements of the total urethral sphincter volume (TSV), rhabdosphincter volume, (RSV) and levator hiatal dimensions (LH) were taken at rest, after voiding.

Twenty-three white and 14 black women (37 in total) were investigated. Subjects did not differ by age or body mass index (BMI). Black women were found to have significantly larger rhabdosphincters (RS) than their white counterparts (8.88 cm(3)  ± 1.65 vs. 5.97 cm(3)  ± 1.82, respectively, P = 0.000). With respect to levator hiatal dimensions at rest, black women had a significantly wider transverse diameter (LHt) than white women (mean difference of LHt = 0.43 cm, 95% CI 0.08-0.78, P < 0.05).

Asymptomatic black nulliparous women have significantly larger rhabdosphincters than their white counterparts. Racial differences in the female urethral morphology could provide an insight on the pathophysiology of stress urinary incontinence.