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Tzu Chi nomograms for uroflowmetry, postvoid residual urine, and lower urinary tract function

Stephen Shei-Dei Yanga, b, Eng-Tzu Shiha, b, Shang-Jen Changa, b

a Department of Urology, Taipei Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, New Taipei, Taiwan
b Department of Urology, School of Medicine, Tzu Chi University, Hualien, Taiwan

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Abstract
The objective of the article is to summarize the results of our previous reports with regard to uroflowmetry, postvoid residual urine (PVR), and lower urinary tract symptoms in healthy children in Xindian, New Taipei, Taiwan. Healthy children aged 4–12 years were enrolled and their PVR was evaluated with two sets of uroflowmetry. Those with a voided volume (VV) < 50 mL were excluded from further analysis. Bladder capacity (BC) was defined as the VV + PVR and the expected BC was defined as (age in years + 1) × 30 mL. Uroflowmetry curves were interpreted independently by two pediatric urologists. The lower value of two consecutive PVRs and the higher value of two consecutive peak flow rates (Qmax) were used to construct dual-PVR and dual-Qmax nomograms, respectively. One parent of each child completed a questionnaire on bedwetting and the dysfunctional voiding symptoms score (DVSS). A total of 1128 children (583 boys and 545 girls) with a mean age of 7.7 ± 2.2 years were eligible for analysis and construction of nomograms. On the first uroflowmetry, 960 (85.1%) children were classified as having a normal bell-shaped curve and 168 (14.9%) had a non–bell-shaped curve. An abnormal uroflow pattern was frequently observed at VV ≥ 100% or BC ≥ 115% of the expected BC. Multivariate analysis revealed that the Qmax value was significantly affected by age, VV, and sex (all p < 0.01). The minimally acceptable Qmax, around the 10th percentile of the dual-Qmax nomogram, was > 11.5 mL/second in children aged ≤ 6 years and > 15.0 mL/second in children aged ≥ 7 years. Significant variations in the PVR were observed in each individual. Multivariate studies showed that the PVR was positively associated with bladder capacity and negatively associated with age, was higher in boys than in girls, and was higher in children with abnormal uroflow patterns. For children aged ≤ 6 years, repetitive PVR > 20 mL or > 10% BC can be regarded as an elevated PVR. For children aged ≥ 7 years, repetitive PVR > 10 mL or 6% BC can be redefined as elevated. A DVSS ≥ 6.66 is highly suggestive of lower urinary tract dysfunction in both sexes with good sensitivity and specificity. New nomograms for uroflowmetry, PVR, and DVSS were established for the noninvasive assessment of pediatric lower urinary tract function. Repeat tests are recommended if a single test is abnormal. Invasive videourodynamic study is recommended in cases of refractory lower urinary tract symptoms and repeat abnormal tests.

Keywords
Children; Lower urinary tract function; Nomogram; Uroflowmetry


 

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