Predicting intrinsic urethral sphincter dysfunction in women with stress urinary incontinence

To determine whether specific clinical characteristics can be used to identify women with stress urinary incontinence due to intrinsic urethral sphincter dysfunction without the aid of urodynamic testing.

A retrospective analysis was performed of 263 consecutive patients who underwent complete urodynamic evaluation for complaints of urinary leakage. Intrinsic sphincter dysfunction was defined as a maximum urethral closure pressure of 20 cm H2O or less in the sitting position at maximum cystometric capacity. Women with sphincter dysfunction were then compared to the group with normal pressure (greater than 20 cm H2O) using t test, chi 2, and logistic regression analyses for 13 clinical indices, endoscopic appearance of the proximal urethra, and eight urodynamic criteria.

The group with intrinsic sphincter dysfunction totaled 132 women (50.2%). Univariate analysis revealed that women in this group were older and were more likely to have undergone a hysterectomy and at least one anti-incontinence procedure compared to the women with normal urethral pressure. However, multivariate analysis revealed that age greater than 50 years was the only independent variable that could predict the presence of intrinsic sphincter dysfunction in women with stress incontinence (odds ratio 1.6, 95% confidence interval 1.2-2.2). The two groups were similar in all other preoperative clinical characteristics.

The only preoperative clinical index that predicted the presence of intrinsic urethral sphincter dysfunction, as defined by low urethral closure pressure, was age over 50 years. In view of previous studies reporting a higher rate of surgical failure in women with low urethral pressure, urodynamic testing should be considered in surgical candidates over age 50 to allow adequate preoperative counseling.