Nocturnal enuresis (NE) is the occurrence of involuntary voiding at night at 5 years, the age when volitional control of micturition is expected. NE may be primary or secondary(1). The role of hypercalciuria in the etiopathogenesis of primary NE has been discussed(2). N - acetyl-beta-D-glucosaminidase (NAG) is a lysosomal enzyme abundantly present in the cells of proximal tubule and is considered a very sensitive marker of renal tubular impairment(3). As increased urinary NAG activity has been reported in patients with hypercalciuria(3), our objective was to evaluate the urinary NAG and calciuria in patients with NE. Fourteen patients (11 boys and 3 girls, mean age 6.8 ± 1.6 yr, range 5- 10 yr) with primary NE were enrolled on basis of the inclusion criteria: age 5-15 yr; absence of urinary tract anomalies; absence of diabetes insipidus and diabetes mellitus; urine osmolality (morning void >400 mOsm/kg); absence of urinary tract infection; no previous treatment for NE; >4 bedwetting episodes within the last 14 days. The blood levels of creatinine, urea, glucose, calcium, sodium, potassium and magnesium and urinary beta-microglobulin were within the normal range. Urinary calcium/creatinine (UCa/Cr; mmol/L : mmol/L) and urinary NAG/creatinine ratios (UNAG/Cr; nkat/L : mmol/L) were assessed in urine collected after the first morning void. To eliminate the influence of age, the obtained results of UCa/Cr and UNAG/Cr were expressed as Z-scores by the equation Z-score = (actual of individual value - mean reference value for age)/standard deviation for age. The reference values were based on previously published data on healthy Czech children(4,5). For statistical evaluation, t-test and linear regression were performed. UCa/Cr values were within the reference range in 13 children, and in only one patient the value exceeded the 95th percentile. The values of UCa/Cr did not differ significantly from the reference data (Table I). In 4 patients the UNAG/Cr values exceeded the age-related 95th percentile range. In the entire group of 14 patients, the UNAG/Cr values were significantly higher compared to reference values (Table I). There was no correlation between UNAG/Cr and UCa/Cr (r = 0.13, P = 0.55). In conclusion, hypercalciuria was not found in children with NE. The presence of elevated urinary levels of UNAG/Cr suggest that tubular dysfunction might be important in patients with enuresis.

UCa/Cr (Z-scores)

0.19 ± 0.92

0 ± 1

0.77*

UNAG/Cr (Z-scores)

1.64 ± 1.65*

0 ± 1

0.003*

* P  compared to reference data(4,5).

Sylva Skalova,
Stepan Kutilek*,
Department of Pediatrics,
Faculty of Medicine Teaching Hospital,
Charles University,
500 05 Hradec Králové, Czech Republic.
E-mail: [email protected]
and
*Center for Clinical and Basic Research,
Pardubice, Czech Republic.

1. Elder JS. Voiding dysfunction. In: Behrman RE, Kliegman RM, Jenson BH, eds. Nelson Textbook of Pediatrics, 17th edn, Philadelphia: WB Saunders 2004; pp 1808-1812.

2. Aceto G, Penza R, Coccioli MS, Palumbo F, Cresta L, Cimador M, et al. Enuresis subtypes based on nocturnal hypercalciuria: A multi-center study. J Urol 2003; 170: 1670-1673.

3. Skalova S, Palicka V, Kutilek S. Bone mineral density and urinary N-acetyl-beta-D-glucos-aminidase activity in pediatric patients with idiopathic hypercalciuria. Nephrology 2005; 10: 99-102.

4. Skalova S, Chladek J. Urinary N-acetyl-beta-D-glucosaminidase activity in healthy children. Nephrology 2004; 9: 19-21.

5. Janda J, Feber J, Sikut M, Carkova S, Smiskova R. Assessment of the urinary calcium/creatinine index in healthy neonates, infants and children. Cs Pediatr 1992; 47: 353-356.