Comparison of Uroflowmetry Time Parameters in Pressure-Flow Study Between Men With Bladder Outflow Obstruction and...

Time parameters are an inherent part of free uroflowmetry and have been used trying to differentiate detrusor underactivity from bladder outflow obstruction (BOO) in men. Since this issue has not been settled, we conducted an exploratory study aimed at comparing uroflowmetry time parameters in pressure-flow study of men with detrusor underactive voiding contraction (DUVC) and BOO, and its relation to PVR volume. As this study is centered on the pathophysiology of voiding, no other clinical variables were examined.

This is a retrospective cross-sectional study of an urodynamics database prospectively acquired from consecutive men aged ≥ 40 years old with non-neurogenic lower urinary tract symptoms in a single tertiary-level hospital. All traces were obtained using water-filled urodynamic equipment, and tests were performed in accordance with the recommendations of the International Continence Society. Pure BOO was defined as a Bladder Outflow Obstruction Index (BOOI = p_detQ_max - 2 Q_max) over 40 and a Detrusor Contraction Index (DCI = p_detQ_max + 5 Q_max) over 100. Pure DUVC was defined as a DCI less than 100 with a BOOI less than 20. Increased PVR volume was defined as ≥ 100 mL. One hundred thirty-six patients had DUVC, who were matched with an equal number of patients with BOO, considering the closest voided volume. Student t-test or Wilcoxon's rank sum test were used to compare pressure-flow study time parameters. The area under the curve (AUC) of the receiver operating characteristic (ROC) analysis was calculated to describe diagnostic accuracy for the diagnosis of DUVC. Statistical significance was defined as two-sided p-value < 0.05.

"Time to maximum flow", "Voiding time", "Time to maximum flow/Voided volume", "Flow time/Voided volume", "Voiding time/Voided volume", "Time to maximum flow/Flow time" and "Time to maximum flow/Voiding time" showed significant differences. The best diagnostic accuracy of parameters not dependent on voided volume for the diagnosis of DUVC versus BOO using AUC of ROC analysis were "Time to maximum flow/Voided volume" (AUC 0.669, p = < 0.001), "Time to maximum flow/Flow time" (AUC 0.654, p = < 0.001) and "Time to maximum flow/Voiding time" (AUC 0.627, p = < 0.001).

This study found significant differences in "Time to maximum flow/Voided volume", "Time to maximum flow/Flow time" and "Time to maximum flow/Voided volume" between men with DUVC and men with BOO matched by the closest voided volume. The results justify further studies for the non-invasive differentiation of these two groups of patients.