Age related nocturnal urine volume and maximum voided volume in healthy children: reappraisal of International Children's Continence Society definitions.

PURPOSE: We determined normal, age related reference data regarding maximum voided volume and nocturnal urine production using the same methodology as in clinical practice. MATERIALS AND METHODS: A total of 62 girls and 86 boys without enuresis (mean +/- SD age 9.64 +/- 2.63 years, range 3 to 15) completed 4 days (2 weekends) of frequency-volume charts and 14 days of home recording of nocturnal urine production. From these recordings maximum voided volume with and without first morning void was derived for each subject. Also, average nocturnal urine volume with and without nocturia was calculated. Percentiles were produced by dividing the population into 1-year age groups. RESULTS: Based on 2,836 daytime voids and 1,977 overnight recordings, maximum voided volume and nocturnal urine volume showed a significant linear relationship with age but not with gender. Maximum voided volume with first morning void was significantly higher than without (403 +/- 137 ml vs 281 +/- 112 ml, p <0.0001) and the 50th percentile line of maximum voided volume with first morning void was 80 to 100 ml higher than Koff's formula (30 x [age + 1] ml). Conversely the 50th percentile of maximum voided volume without first morning void was almost identical to Koff's formula. Regarding nocturnal measurements, nocturia was noted on 128 nights (6.5%) and nocturnal urine volume on nights with nocturia was significantly higher than on nights without nocturia (365 +/- 160 ml vs 248 +/- 75 ml, respectively, p <0.0001). The 97.5th nocturnal urine volume percentile line of healthy children deviated markedly from the current International Children's Continence Society 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 International Children's Continence Society formula for nocturnal polyuria (nocturnal urine volume greater than 130% of maximum voided volume for age), and instead we propose the formula, nocturnal urine volume greater than 20 x (age + 9) ml.

Monosymptomatic nocturnal enuresis is associated with abnormal nocturnal bladder emptying.

PURPOSE: We investigate the nature of enuresis episodes in monosymptomatic nocturnal enuresis using a fluid provocation model. MATERIALS AND METHODS: The study included 18 children 7 to 13 years old with monosymptomatic nocturnal enuresis. Based on basal home recordings patients were subgrouped into those with a normal nocturnal urine output and those with nocturnal polyuria (mean nocturnal urine production on wet nights exceeding 130% of functional bladder capacity, normal functional bladder capacity for age provided). Children were admitted to the hospital for 4 consecutive nights. After an adaptation night all children received orally 25 ml/kg water, 30 minutes before bedtime on the remaining 3 nights. A cordless alarm device enabled registration of enuretic episodes from another room and diapers allowed the measurement of enuresis volumes. Post-void residual volumes were measured by ultrasound. Pelvic floor electromyography was continuously recorded throughout the night, and its association to bladder emptying was investigated. RESULTS: A total of 95 enuresis and 14 nocturia episodes were recorded. Significantly more enuresis episodes were registered on nights with oral fluid load, whereas no increase in number of nocturia episodes was seen. Of the enuresis episodes 46 were associated with incomplete bladder emptying (post-void residual volume greater than 10% of total bladder volume at time of enuresis). No difference between patient groups regarding post-void residual volume was seen. Abnormal bursts of electromyography activity were associated with incomplete micturitions. CONCLUSIONS: Enuresis nocturna episodes in polyuric and nonpolyuric patients are frequently incomplete micturitions. The present findings question the definition of nocturnal enuresis episode as normal complete voiding.