Abnormal urethral motor function is common in female stress, mixed, and urge incontinence

To investigate the urethral motor function in incontinent women.

The intraurethral pressure was measured continuously in the high-pressure zone of the urethra at rest and during repeated short squeezes around the microtip transducer catheter in a group of 205 women with clinically manifest urinary incontinence (severe), and compared with the findings of investigations in 87 middle-aged women (53-63 years) with treatment naïve incontinence (mild-to-moderate) and healthy controls.

Women with established incontinence significantly (P < 0.001) more often (66%) had a pressure fall during or immediately following squeeze than women with treatment naïve incontinence (35%) or asymptomatic women (25%). The acceleration of urinary flow and the maximal flow rate were significantly (P < 0.01) increased in patients with incontinence: acceleration was 13 +/- 2.2 (17.8), 20 +/- 2.8 (18.9), and 32 +/- 4.9 (24.9) degrees (mean +/- SEM; SD) for incontinence, naïve incontinence and no incontinence, respectively; maximum urinary flow rate was 23, 22, and 16 ml/sec. No statistical differences in any of these measures were seen when stress and urge incontinence were compared.

Women with stress, urge, and mixed urinary incontinence seem to have a primary neuromuscular disorder in the urethra, which presents itself as an overactive opening mechanism with a urethral pressure fall instead of a pressure increase on provocation during the filling phase of the bladder, and during bladder emptying a more efficient opening of the bladder outlet than in normal women. We suggest that one and the same pathophysiological mechanism participates in female stress, urge, and mixed incontinence.