To evaluate the relationship between voiding efficiency (VE), International Continence Society (ICS) Bladder Outlet Obstruction Index (ICS-BOOI) and ICS bladder contractility index (BCI), calculated through pressure-flow studies (PFS), in men presenting with male lower urinary tract symptoms (LUTS).

After ethical approval, the data of male patients who presented with male LUTS refractory to medical and conservative treatment between January 2018 and February 2025 were retrospectively evaluated. Patients who were assessed at two institutions were included in the study. Filling cystometry and pressure-flow studies were performed in accordance with the International Continence Society (ICS) standards, based on the criteria outlined in the European Association of Urology (EAU) guidelines. (1). Patients over the age of 45 with unremarkable neurological workup were included. Patient age, prostate volume (as measured by ultrasonography, and diabetes mellitus (DM) status were recorded. Post-void residual (PVR) volumes were measured using suprapubic ultrasound after uroflowmetry. VE was calculated using the formula VE = (VV / (VV + PVR)) × 100, where VV represents the voided volume in uroflowmetry(2).
Based on PFS findings, ICS- BOOI and ICS-BCI were calculated using the following formulas: ICS-BOOI = Pdet@Qmax - 2 × Qmax and ICS-BCI = Pdet@Qmax + 5 × Qmax(2, 3). Patients were categorized into obstructive (ICS-BOOI > 40) and non-obstructive (BOOI ≤ 40) groups based on ICS-BOOI values. Similarly, based on ICS-BCI values, they were classified as adequate contractility (ICS-BCI ≥ 100) and insufficient contractility (ICS-BCI < 100) (3). Patients were compared separately in terms of demographic and clinical characteristics based on bladder contractility (BC) and bladder outlet obstruction (BOO) categories.
Statistical analyses were performed using the latest version of IBM SPSS Statistics software (SPSS 28.0). Independent sample t-tests were used to determine differences between groups, and ROC analysis was conducted. The Youden Index was utilized to determine the optimal cutoff point.

The study included 143 male patients, with a median age of 68 years (range: 45–95, IQR: 18) and a median prostate volume of 41 mL (range: 15–140, IQR: 32). DM was present in 32 patients (22.3%). The median PVR was 140 mL (range: 10–700, IQR: 245), and the median VE value was 65% (range: 10–99, IQR: 32). A comparative evaluation based on ICS-BOOI and ICS-BCI results is summarized in Table 1.

No significant relationship was found between PVR and/or VE and ICS-BOOI values. In the PFS, patients with adequate bladder contractility (ICS-BCI ≥ 100) had significantly different PVR and VE values compared to those with insufficient contractility (ICS-BCI < 100). However, the negative correlation between PVR and ICS-BCI could not be confirmed by ROC analysis (p = 0.2). For the statistically significant difference observed in the VE-ICS-BCI relationship, the optimal VE cutoff value was determined as 74.4% (AUC = 64, p < 0.001, sensitivity 55.3%, specifity 70.2%) (Figure 1).

In male patients over the age of 45 presenting with male LUTS and no significant neurological findings, PVR and VE were not found to be reliable predictors of BOO. However, our findings suggest that VE may serve as an indicator of BC. Specifically, patients with a VE of 74% or higher were more likely to exhibit sufficient bladder contractility (ICS-BCI ≥ 100). Further prospective studies with larger patient populations are necessary to validate these findings and refine the clinical utility of VE in assessing bladder contractility.

Rosier P, Schaefer W, Lose G, Goldman HB, Guralnick M, Eustice S, et al. International Continence Society Good Urodynamic Practices and Terms 2016: Urodynamics, uroflowmetry, cystometry, and pressure-flow study. Neurourol Urodyn. 2017;36(5):1243-60.
Abrams P. Bladder outlet obstruction index, bladder contractility index and bladder voiding efficiency: three simple indices to define bladder voiding function. BJU Int. 1999;84(1):14-5.
Peter F.W.M. Rosier a, Andrew Gammie b, Juan Pablo Valdevenito c, John Speich d, Phillip Smith e,1, Sanjay Sinha f, The Members of the ICS Working Group PFS23. ICS-SUFU standard: Theory, terms, and recommendations for pressure-flow studies performance, analysis, and reporting, Part 2: Analysis of PFS, reporting, and diagnosis. Continence. 2023;7.