Misleading Metrics? A Prospective Study on Post-Void Residual Urine Measurement Timing in Men With Lower Urinary Tract Symptoms

Objective: This study investigates the potential discrepancy between post-void residual urine (PVR) measurements obtained immediately after uroflowmetry and those reflecting patients’ usual voiding patterns, aiming to evaluate the reliability of immediate post-test measurements.Methods: This prospective study included 110 men >45 years with lower urinary tract symptoms. PVR was measured by transabdominal ultrasonography immediately after uroflowmetry (PVR0), on day 1 (PVR1), and day 7 (PVR7). Patients were grouped by pre-void bladder volume: <300 mL, 300–500 mL, >500 mL. Uroflowmetric parameters, prostate volume, PSA, IPSS, BMI, and detrusor thickness were recorded.Results: The mean age was 60.32±6.93 years; mean prostate volume 44.84±20.44 mL. In the uroflowmetry test, the mean values for Qmax, Qave, and voided volume were detected as 15.83±7.00 mL/sec, 6.21±2.62 mL/sec, and 304.15±157.81 mL, respectively. The mean bladder volume was 408.30±191.53 mL. When stratified into three groups based on bladder volume (<300 mL, 300–500 mL, and >500 mL), 26.4% of the patients had a bladder volume <300 mL, 49.1% had 300–500 mL, and 24.5% had >500 mL. The mean PVR0, PVR1, and PVR7 were 104.12±108.51 mL, 33.74±82.54 mL, and 19.59±47.91 mL, respectively. A comparative analysis of PVR0, PVR1, and PVR7 revealed a statistically significant decreasing trend over time: PVR7 < PVR1 < PVR0 (PVR0 vs. PVR1, p < 0.001; PVR0 vs. PVR7, p < 0.001; PVR1 vs. PVR7, p = 0.003).Conclusions: Measuring PVR at a scheduled time after natural bladder filling may yield more accurate and clinically representative data, supporting more reliable treatment planning.