Functional bladder capacity and urine osmolality in children with primary monosymptomatic nocturnal enuresis

Abstract

Objective To assess functional day-time bladder capacity (DBC) and urine osmolality in children with primary monosymptomatic nocturnal enuresis (PMNE) according to age and sex. Material and methods A total of 263 children with PMNE were divided into two groups: Group I, 160 children (63 girls, 97 boys) aged 5–9 years (mean age 7.14±1.47 years); and Ggroup II, 103 children (25 girls, 78 boys) aged 10–15 years (mean age 12.26±1.52 years). DBC (milliliters) was the largest void of the day measured over four 24-h periods, irrespective of the diet applied. Urine osmolality was determined three times: in the evening before bed-time; at night, 2–4 h after falling asleep; and in the morning in the nocturnal void. Results DBC was smaller in Group I than in Group II (151.27 vs 199.46 ml; p<0.05). No statistically significant differences were found in relation to sex (p>0.05). The mean osmolality of the nocturnal void in the morning was 854.15 and 909.22 mOsmol/kg H₂O in Groups I and II, respectively (p>0.05). Differences between boys and girls were not statistically significant (p>0.05). No correlation was found between DBC and urine osmolality (p>0.05). A detailed analysis of the results revealed DBC below the 5th percentile or above the 95th percentile in 23/263 cases (8.7%), reduced osmolality (< 800 mOsmol/kg H₂O) in 76/263 (28.8%), a familial nature of nocturnal enuresis in 124/263 (47.1%) and difficulty waking in 86/263 (32.7%). Conclusions In children with PMNE aged 5–15 years, functional DBC increases with age and does not differ between the sexes; the mean nocturnal urine osmolality is neither age- nor sex-dependent.

• Children
• functional bladder capacity
• nocturnal enuresis
• urine osmolality