Pathogenesis of urethral funneling in women with stress urinary incontinence assessed by introital ultrasound

OBJECTIVE

The incidence of urethral funneling (UF) seen in women with stress urinary incontinence (SUI) during straining is reported to range from 18.6% to 97.4%. Its morphologic basis is unknown. The aim of the present study was to determine whether SUI patients with and without UF differ in terms of history, urodynamic results and magnetic resonance imaging (MRI) findings.

PATIENTS AND METHODS

Fifty-four women (mean age 52 +/- 11 years) with a history of SUI confirmed by clinical and urodynamic findings were included in the study. UF was demonstrated by introital ultrasound performed at a bladder filling volume of 300 mL during maximal straining. MRI for assessment of the urethra, levator ani muscle and endopelvic fascia was performed using axial proton-density-weighted sequences.

RESULTS

UF was demonstrated by introital ultrasound in 59% of the patients with SUI (Group 1) and was absent in 41% (Group 2). There were no differences between the two groups in mean age (P = 0.208), the incidence of mild prolapse of the anterior vaginal wall (Aa, Ba; stage I; P = 0.741), and urodynamic parameters (urethral closure pressure at rest; P = 0.507). The percentages of nulliparous and parous women were 22% and 78% in Group 1 and 54% and 46% in Group 2 (P = 0.013). The two groups did not differ in the MRI demonstration of morphologic defects of the urethra, levator ani muscle and endopelvic fascia or of combined defects.

CONCLUSIONS

The results of the present study did not elucidate the pathogenesis of UF. The demonstration of UF crucially depends on the examination technique employed.