Normal postvoid residual urine in healthy adults

To establish a normal reference value of postvoid residual (PVR) urine volume in "healthy" adults.

Adults were recruited to undergo uroflowmetry and PVR. Those with neurological disorders, malignancy, diabetes, known lower urinary tract dysfunction, and urinary tract infection within the previous 3 months, were excluded from the study. Constipation was defined as Rome IV ≥ 2.

Of the 883 adults enrolled in this study, 194 (22.3%) did not complete the questionnaires or perform the uroflowmetry, 103 (11.7%) met ≥1 exclusion criteria and thus were excluded. In addition, 30 and 38 uroflowmetry were excluded due to artifacts and low bladder volume (BV) (<100 mL), respectively. Finally, 515 uroflowmetry and PVR data from adults aged 36-89 (mean: 59.0 ± 9.5) were examined. There was a significant nonlinear relationship between BV and PVR (p < 0.05), with PVR significantly increased when BV was around 528 mL. Women had lower PVR than men (p < 0.05). PVR also increased as the International Prostatic Symptom Score (IPSS) increased. PVR was unaffected by age and functional constipation. A multivariate analysis revealed that BV (p < 0.05) and IPSS (p < 0.05) had significant influence on PVR, but age, gender, and Rome IV score did not. The 90th and 95th percentiles of PVR for men were 73.2 mL (25% of BV) and 102.6 mL (30% of BV), respectively, while for women they were 60.5 mL (21% of BV) and 93.8 mL (27% of BV), respectively.

Women had lower PVR than men. The 90th percentile or 95th percentile of normal adults' PVR may serve as the upper limit of normal PVR, and readings above this level may necessitate additional evaluation and treatment. Further studies are required to substantiate these recommendations.