Factors associated with voiding function in women with lower urinary tract symptoms: a mathematic model explanation

The aim of this study was to explore the relationship between voiding function and factors such as age, gravidity, parity, menopause, and anterior vaginal wall relaxation.

One hundred twenty-five women were identified from urodynamic records, 83 premenopausal and 42 postmenopausal. All had had a sonographic assessment of the lower urinary tract and a full urodynamic study, including a pressure-flow study. None had diabetes mellitus, overt neurologic disease, pelvic surgery, anticholinergic medication or estrogen therapy, or voiding difficulty symptoms. Voiding parameters included the following urodynamic variables: maximum flow rate, average flow rate, residual urine, the ratio of residual urine to total bladder volume on spontaneous uroflowmetry, maximum flow rate, and detrusor pressure at maximum flow on a pressure-flow study.

Uroflow rates were significantly correlated with age, parity, and urethral mobility. As a whole, the scatter plots of maximum and average flow rates versus voided volume on uroflowmetry displayed a significant correlation (P < 0.0001 and P < 0.0001, respectively). But, there was no association between maximum flow rate and detrusor pressure at maximum flow in the pressure flow study (P = 0.132). Age, menopause, parity, and urethral mobility may have affected the correlation on uroflowmetry but have no effect on pressure-flow plot. On subgroup analysis, significant correlation was identified only in women aged between 30 and 70, with parity greater than three, and urethral mobility greater than 70 degrees. These groups all had a reduced urethral pressure profile.

Age, menopause, parity, and urethral mobility may change the hydrodynamics of the lower urinary tract and have varying impact on the voiding function by altering urethral distensibility. Moreover, poor detrusor power in the postmenopausal women may complicate the analysis of voiding function.