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

健康青少年的膀胱餘尿量

Lim Li Yi^1,2、Shang-Jen CHANG, Stephen Shei Dei Yang¹

林利憶^1,2，張尚任³，楊緒棣¹

1. Division of Urology, Department of Surgery, Taipei Tzu Chi Hospital, New Ta)ipei, Taiwan （臺北慈濟醫院泌尿科）;
2. Unit Urology，Department of Surgery, Hospital Canselor Tuanku Muhriz (馬來西亞囯大醫院泌尿科)
3. Department of urology, National Taiwan University, Taipei, Taiwan （臺大醫院泌尿科）

Purpose: 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. Hence, the objective of this study is to establish age- and gender-specific normal PVR urine volume in adolescents.

Material and Methods: 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.

Results: A total of 1050 adolescents were invited, but only 651 consented. Fourteen participants were excluded due to low bladder volume (BV<100ml) in both assessments (n = 12), BV<100ml 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 <100ml (n=27), PVR >100ml (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 90^th percentile, i.e., PVR >20ml (7% BV) for males of both the age groups, and PVR >25ml (9% BV) and PVR >35ml (>10% BV) for females aged 12-14 and 15-18 years, respectively. Further investigation may be warranted if the repeat PVR is above the 95^th percentile, i.e., PVR >30ml (8% BV) and >30ml (11% BV) for males aged 12-14 and 15-18 years, respectively, and PVR >35ml (11% BV) and >45ml (13% BV) for females aged 12-14 and 15-18 years, respectively.

Conclusion: 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.