Urethral sphincter morphology and function with and without stress incontinence

Area of Science:

• Urogynecology
• Pelvic Floor Imaging
• Female Pelvic Medicine

Background:

• Stress urinary incontinence (SUI) significantly impacts women's quality of life.
• Understanding the anatomical and functional correlates of SUI is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the relationship between urethral sphincter anatomy, urethral function, and pelvic floor muscle function in women with and without SUI.
• To determine if magnetic resonance imaging (MRI) can identify structural differences in the striated urogenital sphincter associated with SUI.

Main Methods:

• 103 women with SUI and 108 asymptomatic controls underwent MRI, urethral profilometry, and vaginal closure force measurement.
• Striated urogenital sphincter (SUS) length, thickness, and area were quantified using MRI.
• A length-area index was calculated as a proxy for SUS volume.

Main Results:

• Women with SUI exhibited a significantly smaller SUS volume (length-area index) compared to controls (p=0.04).
• No significant differences were found in SUS length, thickness, or area between the groups.
• SUS dimensions and volume correlated with urethral axis elevation and increased vaginal closure force during voluntary pelvic muscle contraction.

Conclusions:

• A smaller striated urogenital sphincter is associated with stress urinary incontinence.
• Reduced SUS size correlates with diminished pelvic floor muscle function, suggesting an anatomical basis for SUI.