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Jornal de Pediatria
On-line version ISSN 1678-4782
PENIDO, Maria Goretti Moreira Guimarães et al. Urinary excretion of calcium, uric acid and citrate in healthy children and adolescents. J. Pediatr. (Rio J.) [online]. 2002, vol.78, n.2, pp. 153-160. ISSN 1678-4782. http://dx.doi.org/10.1590/S0021-75572002000200015.
Objective: to obtain regional reference values for calcium, uric acid and citrate urinary excretion and establish a correlation between those excretions in 24-hour urine sample and single urine sample for their use in clinical practice. Methods: a hundred and twenty-five healthy children and adolescents were randomly chosen and submitted to the following protocol: clinical examination, biochemical analysis of blood, blood cell count, parathormone, 24-hour urine, fasting urine sample and stool test.Results: the maximum value of calcium excretion in 24-hour urine was 3.75mg/kg; in mg/dl of the glomerular filtration rate, it was 0.10; and for the calcium/creatinine (mg/dl) ratio in the fasting urine sample was 0.25. Positive correlation was observed between calcium excretion in the 24-hour urine and the fasting sample (mg/dl and mg/dl of glomerular filtration rate). The maximum values of uric acid excretion in 24-hour urine were 600, 450, and 320mg and 13, 15 and 18mg/kg for adolescents, school and preschool children, respectively; in mg/dl of glomerular filtration rate, in the fasting urine sample, it was 0.47. Positive correlation was observed for the uric acid excretion in 24-hour urine and fasting urine samples. The mean values for the citrate excretion in 24-hour urine were 1.6, 1.1 and 0.5mmol for adolescents, school and preschool children, respectively; for citrate/creatinine ratio, in the fasting urine sample the mean value was 0.3.Conclusions: the calcium and uric acid excretion in 24-hour urine showed correlation with those in the fasting urine sample, which allows their use for metabolic diagnosis, population studies and follow-up of patients with hypercalciuria and hyperuricosuria without voiding control; the citrate/creatinine ratio in the fasting urine sample can be used for controlling patients with hypocitraturia.
Keywords : calcium; uric acid; citrate and urinary excretion.