Beyond the Abstract - Relationship between proximal urethrovaginal space thickness and detrusor overactivity in women with stress urinary incontinence, by Ji Yun Chae

BERKELEY, CA (UroToday.com) - Detrusor overactivity (DO) has been proven through objective evaluation with urodynamic study (UDS), and not all mixed urinary incontinence (MUI) patients exhibit DO on UDS.

When urinary incontinence is combined with DO, the patient’s quality of life decreases markedly and the efficacy and satisfaction with anti-incontinence surgery decline. We previously reported that women with MUI associated with DO had shown no difference in demographic and clinical variables before anti-incontinence surgery, but experience less satisfaction after surgery when compared with those without DO.

The reason for the difficulty of DO’s reproducibility in stress urinary incontinence (SUI) is that SUI might also be the primary pathophysiologic mechanism responsible for MUI. In these women, the incompetent urethral sphincter and bladder neck allow urine to enter the proximal urethra during physical activity, eliciting an urethro-detrusor facilitative reflex that triggers involuntary detrusor contraction, causing urgency and urge urinary incontinence (UUI). So, there is a clinical discrepancy with symptomatic MUI and actual presentation of DO on UDS.

On the other hand, there is a lack of research on the relations between DO and female anatomical structures. The aim of this study was to investigate whether female anatomical variables such as urethrovaginal space (UVS) thickness and urethral length (UL), are major factors that exert influence on DO in women with SUI. Prospective data was collected from 72 women with SUI who underwent the mid-urethral sling operation. The subjects were divided into 2 groups according to the presence of DO by preoperative UDS. UVS was measured by trans-vaginal ultrasound. UL was measured by using a urethral catheter and a ruler. UVS, UL, Q-tip, and urodynamic parameters, such as maximal urethral closure pressure (MUCP) and valsalva leak point pressure (VLPP) were compared between the two groups.

Of 72 women, 23 patients had DO (31.9%). Proximal UVS was significantly thinner (p<0.001) and MUCP was significantly lower (p=0.008) in women with DO. According to the receiver operating characteristic (ROC) curve based DO prediction, the best cutoff value for UVS was 0.84 cm (area under ROC curve: 0.763).

In this study, proximal UVS was significantly thinner and MUCP was significantly lower in patients with DO. A proximal UVS of less than 0.84 cm was shown to be a predictive parameter for the development of DO on pre-operative UDS.

There are several limitations of our study. First, a relatively small number of patients render it challenging to define the exact role of UVS and UL. Second, we utilized one experimenter to conduct and interpret measurement of UVS thickness and measurement of UL in order to reduce inter-individual errors. However, proximal UVS thickness (cm) showed 2mm difference for the average value even though there was statistical difference between the group with DO which was 0.5±0.2 vs. the group without DO which was 0.7±0.2, and this is an error that can occur according to what degree the experimenter pulls urethral catheter. The methods of measuring UVS and UL should be validated by another method, such as magnetic resonance imaging (MRI), but in clinical practice it is not easy to perform MRI in SUI patients.

The objective of this study was to characterize MUI in relation to DO using UVS and UL by means of a relatively simple method. Large-scaled prospective studies are needed to determine the critical role of UVS and UL in patients with DO.

Written by:
Ji Yun Chae as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

Relationship between proximal urethrovaginal space thickness and detrusor overactivity in women with stress urinary incontinence - Abstract

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