The definition of mixed urinary incontinence (MUI) of the International Continence Society exclusively assesses patient-reported symptoms without consideration of physical and urodynamic results, what is inadequate to reliably predict the pathophysiology of the underlying pathology. We investigated and compared clinical and urodynamic findings in women with MUI and assessed predictive variables for the different MUI clinical presentations.

In a national, multicentre, prospective study, women presenting with a clinical history of MUI were classified into 3 sub-groups: stress-predominant or urge-predominant MUI (S-MUI; U-MUI) or MUI with equal symptoms’ presentations (E-MUI). All patients underwent physical examination, with the evaluation of urethral mobility and the provocative stress test, the 3-day voiding diary, the no. of daily pads used, and urodynamics with pressure flow-study. Clinical subjective and objective findings of the 3 sub-groups of patients were compared with the underlying urodynamic dysfunction. A multivariate, logistic, regression analysis was applied to identify predictive variables for the different MUI sub-groups.

144 women were prospectively included and evaluated: 74 presented with predominant S-MUI, 67 with predominant U-MUI, 3 with E-MUI (the latter were excluded from the statistical analysis). Table 1 shows the results of the comparison on clinical history and urodynamic findings between S-MUI and U-MUI sub-groups. With regards to the clinical and urodynamic variables associated with the two sub-components of MUI, daytime and night-time urinary frequency, maximum pressure of uninhibited detrusor contractions, opening detrusor pressure and detrusor pressure at maximum flow rate were significantly higher in U-MUI, while the no. of daily pads and maximum cystometric capacity were significantly higher in S-MUI. The clinical and urodynamic predictive variables for the 2 MUI sub-groups are showed in Table 2.

In women with a history of MUI at presentation, clinical history alone corresponds to the supposed, underlying coexistence of detrusor overactivity with urodynamic SUI in only about half of cases. High proportions of MUI patients on urodynamic evaluation present with urodynamic stress incontinence alone (28.4%) or with isolated detrusor overactivity (21.5%). About 17% of MUI cases do not show any dysfunction on urodynamics and probably they should deserve an ambulatory urodynamic monitoring, although a diagnosis of hypersensitive bladder could not be excluded in these cases. Objective physical findings can help confirming the clinical diagnosis of predominant S-MUI, such as the detection of urethral hypermobility and positive provocative stress test. At history, only the presence of nocturia appears to be a reliable predictive factor for predominant U-MUI.

Confounding clinical sign/symptom combination can be found in women with MUI, and without a precise definition or understanding of the role of the stress and urge subcomponents, the assessment of an intervention for MUI remains challenging. History alone cannot be useful in well characterizing MUI and in directing appropriate treatment strategies; some findings during the physical examination appear to be predictive factors specifically for the diagnosis of predominant S-MUI, but it is the urodynamic investigation that more appropriately reflects bladder and sphincter behaviour in patients affected by MUI.

Chughtai B, Laor L, Dunphy C, Lee R, Te A, Kaplan S. Diagnosis, Evaluation, and Treatment of Mixed Urinary Incontinence in Women. Rev Urol. 2015;17:78-83.
Brubaker L, Stoddard A, Richter H, et al. Mixed incontinence: comparing definitions in women having stress incontinence surgery. Neurourol Urodyn. 2009; 28:268–273.