Urodynamic and clinical features in women with overactive bladder: When to suspect concomitant voiding dysfunction?

The aim of this study is to describe the prevalence and type of female voiding dysfunction (FVD) in patients with overactive bladder (OAB) who were studied by urodynamics and its relationship with voiding symptoms.

This is a cross-sectional study of female adult patients with OAB syndrome who underwent UDS in a University Hospital in Chile between January 2015 and April 2020. FVD was defined either as bladder outlet obstruction (BOO) or detrusor underactivity (DU). BOO was established if the Solomon-Greenwell BOO index was higher than 18. DU was diagnosed when the invasive maximum flow rate (Qmax) was ≤15 ml/sec, detrusor pressure at Qmax (Pdet@Qmax) was ≤20 cmH₂ O and postvoid residual (PVR) was greater than 10%. Urodynamic data and clinical features were compared between groups.

Two hundred and ninety-nine UDS were selected and analyzed. Bladder outlet obstruction was diagnosed in 59 patients (19.7%), whereas DU was found in 10 patients (3.3%). In the multivariate analysis, the logistic regression to predict BOO demonstrated that night-time frequency, the presence of detrusor overactivity and a higher PVR were independent predictors of BOO. Instead, for DU, the only independent predictor was a smaller voided volume in the pressure-flow study.

Female voiding dysfunction was found in 23% of patients with overactive bladder. BOO is more frequent than DU, and should be suspected in patients with higher night-time frequency, presence of detrusor overactivity and a high PVR. Instead, DU should be suspected in patients with a smaller voided volume.