Abstract

Introduction: The aetiology of urinary incontinence is multifactorial. There are ultrasound parameters that define continence risk factors. The synergism of the abdominoperineal muscles may be lost in incontinent patients, and it is unknown what role the transversus abdominis plays in maintaining urinary continence. The aim is to assess whether the thickness of the transversus abdominis muscle can be a predictive factor of continence in premenopausal women.
Material and method: A prospective case-control study was conducted among 515 women (48.5%) incontinent, 51.5% continent. The thickness of the participants’ transversus abdominis was measured using bidimensional ultrasound on the abdominal wall. To assess synergistic contraction, the same measurements were taken at rest, and again after 3-4 seconds of maximum perineal muscle contraction in the supine position while slightly flexing the knees.

The intraclass correlation coefficient for the ultrasound variables was calculated. A bivariate analysis of the demographic and ultrasound variables under study was carried out, followed by a multivariate analysis.
Results: 515 women were assessed: 48.5% incontinent, 51.5% continent. Abdominoperineal physiological co-contraction was identified in all of them (except one with Oxford=0). The intraclass correlation coefficient of the TTR was 0.94, and of the TTC, 0.93 (p=0.00). The TTR tended to be higher in incontinent women (0.32; SD 0.11) versus continent women (0.30; SD 0.11) (p>0.05). TTC tended to be higher in 81 continent women (0.54; SD 0.19) versus incontinent women (0.53; SD 0.20) (p>0.05), and the RatioT was higher in continent women (85.07; SD 63.4) versus incontinent women (75.5; SD 61.74) (p<0.05) in bivariate analysis. The ultrasonographic variables of the transverse thicknesses were not shown as an independent continence predictor during the multivariate analysis.
Conclusion: The procedure for measuring the thickness of the transversus abdominis thickness is simple and easily reproducible. Both continent and incontinent women experience synergistic abdominoperineal contraction. The TTC tends to be higher in continent women, as does the RatioT, while the transversus abdominis thickness cannot be defined as an independent predictor of continence in premenopausal women.

Keywords:Pelvic floor muscle; Urinary incontinence; Transversus abdominis; Ultrasound measure; Women

Abbreviations: TA: Transversus Abdominis Muscles; PFM: Pelvic Floor Muscles; TTR: Transversus Thickness at Rest; TTC: Transversus Thickness at Contraction; ICIQ-SF: International Consultation of Incontinence Questionnaire-Short Form; 2D US: Bidimensional Ultrasound; ICC: Intraclass Correlation Coefficient; UUI: Urgency Urinary Incontinence; SUI: Stress Urinary Incontinence; MUI: Mixed Urinary Incontinence; UI: Urinary Incontinence; IAP: Intra- Abdominal Pressure
Key Message: The transversus abdominis muscle cannot be defined as an independent predictor of continence in premenopausal women.