The aim of this study is to evaluate the prevalence of voiding dysfunction (VD) in females with overactive
bladder (OAB) and its relationship with voiding symptoms. We hypothesize that VD is a frequent finding in this group and that certain clinical features should ensure its active ruling out.

This is a cross-sectional study. We reviewed urodynamic studies performed from 2015 to 2018 in a
university hospital in Chile. Urodynamics were conducted following ICS good practices. Female adult
patients with OAB syndrome were selected. Patients with previous incontinence or radical pelvic surgery,
use of anticholinergic treatment, high-grade pelvic organ prolapse (higher than stage II), bladder cancer,
urinary tract calculi, neurogenic bladder, and painful bladder syndrome were excluded. Patients without
results of flow-pressure study were also excluded. VD was defined either as bladder outlet obstruction
(BOO) or detrusor underactivity (DU). BOO was established with the Solomon-Greenwell BOO index (1)
(BOOIf) higher than 18. DU was diagnosed with all Qmax≤15 ml/sec, PdetQmax ≤20 cmH2O and PVR
>10% (2). Urodynamic data and clinical features were compared between groups. Numerical variables
were analyzed with non-parametric tests, and Chi-square was used to compare categorical variables.
Data was processed using IBM SPSS version 23.0 and two tailed p-values <0.05 was considered as
statistically significant.

One thousand two hundred and sixty six (1266) urodynamic studies were reviewed, 235 were selected and analyzed. Mean age was 55.9±12.6 years, patients had 2 (IQ 0-3) vaginal deliveries, 34% had diabetes and 37% had previous hysterectomy.
Demographic and symptomatic characteristics are listed in Table 1. Additionally, 10.2% reported
symptoms of vaginal bulge and 89.2% had mixed urinary incontinence. Urodynamic characteristics are
listed in Table 2. BOO was found in 43 (18.2%) while 7 patients (2.9%) had DU. Detrusor overactivity during
filling cystometry was found in 47.2%. Urodynamic stress test was positive in 78.7% of cases, with median
ALPP of 100 cmH20 (IQ 73-138), and 23.4% had Valsalva-induced detrusor overactivity. Four out of 7
and 32 out of 43 of patients with DU and BOO respectively, had concomitant urodynamic detrusor
overactivity. In the bivariate comparison, BOO was associated with night-time frequency, reduced voided
volume, higher presence of detrusor overactivity and greater PVR. Moreover, DU was associated with
higher day-time frequency and intermittency. In the multivariate analysis these factors were predictors or
BOO/DU even adjusted by age, diabetes, vaginal bulge and previous hysterectomy.

Even using strict definitions for BOO and DU, a considerable proportion of female patients with OAB
present concomitant voiding dysfunction (21.2%), this is mostly explained by outlet obstruction. BOO is a
well-known contributing factor to urgency, and it is clear that it must be addressed to engage in proper
management of these patients. Our study confirms the presence of mixed storage and voiding
dysfunction, showing that a small subset of patients has either DO-DU and must be suspected in patients
with high frequency and intermittency, or DO-BOO that must be considered in patients with high PVR and
frequency. Being frequency part of the definition of OAB we think every patient should have a
dysfunctional voiding ruled out with at least a free uroflowmetry and PVR. The use of a rigorous definition
of DU resulted in a small number of patients being allocated to that group (n=7). For this reason, many
variables with evident differences did not result in statistical significance (voided volume and ALPP).
Being unaware of the presence of a VD could be detrimental for patient’s treatment. This information is
paramount when taking care of a patient with OAB, and must be considered especially in refractory
patients.

Voiding dysfunction is a prevalent condition in the female OAB population. Clinicians should have high
suspicion of VD especially in patients presenting with elevated PVR, high urinary frequency, and
intermittency. These findings may prompt further study with urodynamics.

Solomon E, Yasmin H, Duffy M, Rashid T, Akinluyi E, Greenwell TJ. Developing and validating a new nomogram for diagnosing bladder outlet obstruction in women. Neurourol Urodyn. 2018;37(1):368–78.
Gammie A, Kaper M, Dorrepaal C, Kos T, Abrams P. Signs and Symptoms of Detrusor Underactivity: An Analysis of Clinical Presentation and Urodynamic Tests From a Large Group of Patients Undergoing Pressure Flow Studies. Eur Urol. 2016 Feb;69(2):361–9.