INTRODUCTION AND OBJECTIVES: The aim was to provide normal age related reference data regarding both MVV and nocturnal urine production using the same methodology as in clinical practice.

METHODS: A total of 148 healthy non-enuretic children aged 9.64 ± 2.63 yrs, (range 3-15 yrs, 62 girls) completed 4 days (2 weekends) of FV charts and 14 days of home registration of nocturnal urine production. From these, MVV with (MVVw) or without (MVVwo) the first morning voided volume included was derived for each subject. Also, average nocturnal urine volume with nocturia nights included (N-Uvolw) or not (N-Uvolwo) was calculated. Percentiles were produced by dividing the population in 1 year age groups.

RESULTS: Based upon 2836 daytime voids and 1977 overnight recordings both MVV and N-Uvol showed a significant linear relationship with age without gender differences. MVVw was significantly higher than MVVwo (403 ± 137 vs. 281 ± 112 ml, p<0.0001) and the 50th percentile line of MVVw was 80-100 ml higher than Koff’s formula (30 x (age + 1)). On-the-other-hand, the 50th percentile of MVVwo was almost identical to Koff’s formula. Regarding nocturnal measurements, nocturia was noted in 128 nights (6.5%) and N-Uvolw was significantly higher than N-Uvolwo (365 ± 160 vs. 248 ± 75 ml, respectively, p < 0.0001). The 97.5th N-Uvol percentile line of healthy children deviated markedly from the current ICC definition of nocturnal polyuria, especially at low and high ages.

CONCLUSIONS: We demonstrate clearly that the universally used formula 30 x (age +1) (ml) is indeed valid for a population of healthy Danish children but only if the first morning void is disregarded. Furthermore, we question the validity of the current ICCS formula for nocturnal polyuria (N-Uvol > 130 % of MVVage) and instead we propose the formula N-Uvol > 20 x (age + 9)(ml).

Source of Funding: Karen Elise Jensen Foundation
Lundbeck Foundation