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Reference values for urinary calcium excretion and screening for hypercalciuria in children and adolescents
Insights
Establishing reference values for urinary calcium/creatinine ratios in children is crucial for understanding hypercalciuria, a risk factor for kidney stones. This study defined normal ranges and identified incidence and subtypes of hypercalciuria in healthy pediatric populations.
Area of Science:
- Pediatric Nephrology
- Urology
- Metabolic Bone Disease
Background:
- Hypercalciuria is a known risk factor for kidney stone disease in children.
- The definition, incidence, and pathogenesis of pediatric hypercalciuria remain controversial.
- Establishing reliable reference values is essential for accurate diagnosis and management.
Purpose of the Study:
- To establish reference values for urinary calcium/creatinine (Ca/Cr) ratios in healthy children.
- To determine the incidence of hypercalciuria in a pediatric cohort.
- To investigate the underlying mechanisms of hypercalciuria in affected children.
Main Methods:
- Measured urinary Ca/Cr ratios in 564 healthy children (aged 6-17.9 years) in fasting and post-absorptive states.
- Assessed Ca/Cr ratios in 1013 children over two consecutive days to determine hypercalciuria incidence.
- Subclassified hypercalciuric children based on fasting Ca/Cr, response to oral calcium load, and sodium excretion.
Main Results:
- Urinary Ca/Cr ratios were independent of age and sex, allowing for common normal ranges.
- Hypercalciuria was identified in 3.8% of the studied children (39 out of 1013).
- Three subtypes were identified: absorptive hypercalciuria (AH), renal hypercalciuria (RH), and dietary hypercalciuria (DH).
Conclusions:
- Defined age- and sex-independent reference ranges for urinary Ca/Cr ratios in children.
- Provided incidence data for hypercalciuria in a large pediatric cohort.
- Characterized distinct subtypes of hypercalciuria, aiding in understanding its pathogenesis and guiding future research.
Abstract:
Hypercalciuria is of continuing interest as one of the risk factors for stone disease in children, but the definition, incidence and pathogenesis are controversial. Therefore reference values for the urinary calcium/creatinine (Ca/Cr) ratios were established in 564 healthy children aged 6-17.9 years during the fasting state (09.00 h) and in 236 of them also in the post-absorptive state about 2 h after lunch (14.00-16.00 h). The Ca/Cr ratios in both urine specimens were independent of age and sex, rendering it possible to determine a common normal range and to calculate centiles for Ca excretion in a large sample of healthy children and adolescents. To provide information about the incidence of hypercalciuria the Ca/Cr ratios of 1013 other apparently healthy children aged 6-17.9 years were measured during the post-absorptive state on two consecutive days. In 39 (3.8%) of them, 21 girls, and 18 boys, the Ca excretion was elevated in both urine specimens. Thirty-six of these children, all presenting without renal complaints, underwent further investigations to elucidate the possible mechanisms of the hypercalciuria. On the basis of the Ca/Cr concentration during the fasting state and the calciuric response to a standardised oral Ca tolerance test the children were subclassified into three groups: (1) Absorptive hypercalciuria (AH, n = 12): Increased calciuric response to the Ca load, but normal fasting Ca/Cr; (2) Renal hypercalciuria (RH, n = 8): Increased Ca/Cr after Ca load and during the fasting state; (3) Normal Ca excretion during the fasting state and after the Ca tolerance test, but increased sodium excretion (dietary hypercalciuria, DH, n = 16).(ABSTRACT TRUNCATED AT 250 WORDS)