The role of invasive urodynamics (UDS) in the diagnostic pathway of lower urinary tract symptoms is controversial. Although the surgical indication rate was shown to not be altered in the UPSTREAM trial [1], the additional information obtained from UDS could still be of value and allow for a better counseling and shared decision-making regarding surgical outcomes. 

We aim to ascertain if  UDS prior to surgery for benign prostatic obstruction (BPO) has predictive value for the surgical outcomes. We also aim to analyze if UDS enables the identification of patients who achieve the best benefit from surgical management.

We performed a retrospective study by reviewing the clinical records of patients submitted, by the same surgeon, to transurethral incision of the prostate (TUIP) and transurethral resection of the prostate (TURP) for BPO between January of 2018 and December of 2023, in whom an invasive urodynamic study had been done prior to surgery. 48 patients with available follow-up data were identified and included for analysis. 

Demographics, clinical variables, uroflowmetry and UDS parameters were collected and analyzed. Patients were categorized according to: i) presence of detrusor overactivity (DO), defined as the occurrence of detrusor contractions during the filling cystometry [2]; ii) Bladder contractility index (BCI), stratified by cutoffs of <100, 100-150 and >150; iii) Bladder outlet obstruction index (BOOI), stratified by cutoffs of <20, 20-40 and >40. The main outcomes studied were improvement of maximum urine flow rate (QMAX) after surgery, measured in mL/s; and reduction of post-void residual (PVR) after surgery, measured in mL. 

Data are presented as: i) absolute and relative frequencies when categorical and ii) mean (m) ± standard deviation (SD) when continuous with normal distribution iii) median (md); interquartile range (IQR) when continuous with non-normal distribution. Analyses were performed using IBM SPSS Statistics v.26 for Windows software (IBM Corp, Armonk, NY).

Complete baseline characteristics of the 48 patients are presented in table 1. Patients were submitted to TURP in 87.5% of cases (42/48).  Age at the time of surgery ranged from 38 to 84 years (mean 63±1.9 years). Pre-operative average QMAX was 10.7±0.79 mL/s and PVR distribution was md: 50; IQR:110 mL. 

DO was identified in 47.9% of the cases (23/48). Presence of DO showed a trend towards a worse QMAX improvement (md: 10mL/s, IQR: 10mL/s vs. md:15mL/S, IQR: 8 mL/s; p= 0,055). However, DO showed no impact in reduction of PVR. The population was then stratified according to BCI and BOOI. In this sub-analysis, DO showed a trend toward worse QMAX improvement (9.8±2.4 mL/s vs. 18±3.3; p=0.069) and worse PVR reduction (md: +30mL, IQR: 20mL vs. md: -30mL; IQR 98mL; p=0.095) in the subgroup of patients with equivocal obstruction (BOOI between 20-40). DO also showed a trend for worse QMAX improvement (md: 9.5mL/s, IQR:10mL/s vs. md:15; IQR: 6mL/s; p=0.088) in the subgroup of patients with a BOOI>40. 

Distribution regarding BCI stratification was: i) <100: 52.1% (25/48); ii) 100-150: 41.7% (20/48); iii) >150: 6.3% (3/48). A BCI of >150 showed an association with better QMAX improvement (14.4±1.7mL/s vs 11.3±1.3mL/s vs 27.7±7.4mL/s; p=0.004) but no impact in PVR reduction. Distribution regarding BOOI was: i) <20: 25% (12/48); ii) 20-40: 35.4% (17/48); iii) 39.6% (19/48). A BOOI of >40 showed a trend toward a better PVR reduction (-17.1±29.6 vs. -22.1± 22.1 vs. -146.5±-46.8; p=0.056) but no impact in QMAX improvement.

Our results suggest that the diagnosis of secondary DO could have predictive value for the outcome of BPO surgery. In fact, the presence of DO in UDS showed a trend towards worse QMAX improvement after the surgery. This finding was also seen in those with equivocal degree of obstruction (BOOI between 20 and 40), a subpopulation of particular interest regarding surgical decision, in which the finding of DO in UDS showed a trend towards not only worse QMAX improvement but also an inferior PVR reduction. Our results  therefore suggest that this subset of patients may have a suboptimal outcome after BPO surgery. 

In parallel, the degree of bladder contractility and the degree of bladder outlet obstruction previous to surgery showed an association with surgical outcomes. Specifically, a higher bladder contractility (defined as BCI>150) showed an association with higher QMAX improvement after surgery and a higher degree of bladder outlet obstruction (defined as BOOI>40) showed a trend towards a greater reduction in PVR after the surgery. These results suggest that these patients have the most benefit from surgical management.

Our results suggest that  invasive urodynamic study prior to BPO surgery may enable the identification of patients that derive the most from surgical management and also, other patients in which the improvement from surgery may be inferior than expected. Therefore, UDS is a valuable diagnostic tool in the management of BPO. Nevertheless, the clinical utility of our findings and the extrapolation for routine use must be further studied.

Drake MJ, Lewis AL, Young GJ, Abrams P, Blair PS, Chapple C, et al. Diagnostic assessment of lower urinary tract symptoms in men considering prostate surgery: A noninferiority randomised controlled trial of Urodynamics in 26 Hospitals. European Urology. 2020 Nov;78(5):701–10. doi:10.1016/j.eururo.2020.06.004
D’Ancona CD, Haylen BT, Oelke M, Herschorn S, Abranches-Monteiro L, Arnold EP, Goldman HB, Hamid R, Homma Y, Marcelissen T, Rademakers K, Schizas A, Singla A, Soto I, Tse V, de Wachter S. An International Continence Society (ICS) Report on the Terminology for Adult Male Lower Urinary Tract and Pelvic Floor Symptoms and Dysfunction. Neurourol Urodyn. 2019 DOI: 10.1002/nau.23897