Age- and gender-specific normal post void residual urine volume in healthy adolescents

Elevated post void residual (PVR) is a significant risk factor for urinary tract infections (UTI). It is also a significant predictor of treatment outcomes in cases of vesicoureteral reflux, pediatric enuresis, and non-neurogenic LUT dysfunction. However, the absence of age-specific nomograms for adolescents may limit PVR's use in clinical practice.

To establish age- and gender-specific normal PVR urine volume in adolescents.

Healthy adolescents aged 12-18 years were recruited to undergo two uroflowmetry and PVR studies whenever they felt the urge to urinate. Adolescents with neurological disorders, known LUT dysfunction or UTI were excluded.

A total of 1050 adolescents were invited, but only 651 consented. Fourteen participants were excluded due to low bladder volume (BV < 100 ml) in both assessments (n = 12), BV < 100 ml in one assessment (n = 1), or failure to provide relevant history (n = 1). From the 1084 uroflowmetry and PVR obtained from 637 adolescents, 190 results were further excluded due to artefacts (n = 152), BV < 100 ml (n = 27), PVR >100 ml (n = 5) and missing information (n = 6). Ultimately, 894 uroflowmetry and PVR from 605 adolescents (mean age 14.6 ± 1.5 years) were analyzed. PVRs were higher in adolescents aged 15-18 years than in those aged 12-14 years (P < 0.001). Moreover, they were higher in females than in males (P < 0.001). Multivariate analysis revealed that PVR was positively influenced by age (P = 0.001) and BV (P < 0.001). The age- and gender-specific percentiles of PVR in ml and percentage of BV were calculated. We recommend a repeat PVR and close monitoring if PVR is above the 90th percentile, i.e., PVR >20 ml (7% BV) for males of both the age groups, and PVR >25 ml (9% BV) and PVR >35 ml (>10% BV) for females aged 12-14 and 15-18 years, respectively. Further investigation may be warranted if the repeat PVR is above the 95th percentile, i.e., PVR >30 ml (8% BV) and >30 ml (11% BV) for males aged 12-14 and 15-18 years, respectively, and PVR >35 ml (11% BV) and >45 ml (13% BV) for females aged 12-14 and 15-18 years, respectively.

PVR increases with age and varies by gender; thus, age-and gender-specific reference values should be used. Further data from other countries is required to determine whether the study's recommendations can be applied globally.