Urodynamic characteristics of mixed urinary incontinence and idiopathic urge urinary incontinence

To evaluate and compare the clinical and urodynamic findings in patients with either mixed urinary incontinence (MUI) or simple urge urinary incontinence (UUI).

A series of 100 consecutive female patients with MUI and UUI were identified from a database. Patients with neurogenic bladder, fistula, urethral diverticulum, prior urologic surgery or known urinary tract obstruction were excluded. All patients were classified according to the urodynamic classification of overactive bladder of Flisser et al. and all patients underwent history, physical examination, validated incontinence questionnaire, 24-hour voiding diary, 24-hour pad test, video urodynamic study (VUDS), and cystoscopy.

A significantly higher proportion of patients with UUI exhibited detrusor overactivity at VUDS, (67% of the patients with UUI vs. 24% of the MUI, P < 0.05). Patients with UUI had fewer episodes of incontinence (6.7 vs. 4.2, P < 0.05) with slightly less objective urine loss (24-hour pad test 94 gm vs. 128 g of loss, P < 0.05) and voided at higher pressures (p(det) at Q(max) 21.4 vs. 15.6 cm H(2)O, P < 0.05). Patients in both groups had functional and urodynamic bladder capacities that were not statistically different.

Women with UUI were more likely to exhibit detrusor overactivity but experienced fewer episodes of incontinence and less urinary loss when compared with women who had MUI. The "urge incontinence" component of MUI appears to be different than that of UUI, and suggests that urge incontinence may be overdiagnosed in patients with SUI who misinterpret their fear of leaking (because of SUI) for urge incontinence.