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Renal function in children with idiopathic hypercalciuria
1Department of Pediatrics, University of Tennessee, Memphis.
Insights
This study found normal renal tubular function in children with idiopathic renal hypercalciuria, suggesting these abnormalities are not present early in the condition. These findings are crucial for understanding pediatric kidney stone disease.
Area of Science:
- Pediatric Nephrology
- Renal Physiology
- Urolithiasis Research
Background:
- Idiopathic renal hypercalciuria (IRH) is linked to renal tubular dysfunction in adults.
- Early detection of tubular abnormalities in pediatric IRH is not well-established.
Purpose of the Study:
- To assess renal tubular function in children diagnosed with idiopathic renal hypercalciuria.
- To determine if tubular abnormalities are present early in the natural history of pediatric IRH.
Main Methods:
- Evaluated ten children (aged 5-17) with IRH (urolithiasis or hematuria).
- Assessed urinary calcium excretion, creatinine clearance, Tm phosphate, fractional excretion of uric acid, sodium, and beta-2-microglobulin.
- Conducted hypotonic diuresis and water deprivation tests after a controlled diet.
Main Results:
- All measured renal tubular functions, including Tm phosphate, fractional excretions, and water handling, were normal in the pediatric IRH group.
- Maximum urinary osmolality during water deprivation was slightly lower than in healthy controls, but overall tubular function remained within normal limits.
Conclusions:
- Renal tubular function appears to be normal in children with idiopathic renal hypercalciuria.
- Abnormalities in renal tubular function may not be an early feature of idiopathic renal hypercalciuria in the pediatric population.
Abstract:
Abnormalities in renal tubular function have been reported in adult patients with idiopathic renal hypercalciuria. To determine if such abnormalities are present early in the natural history of renal hypercalciuria, we evaluated renal tubular function in ten children with idiopathic renal hypercalciuria, aged 5-17 years. Seven of the children presented with urolithiasis and three with hematuria. Urinary calcium excretion ranged from 4 to 9 mg/kg per day, (5.2 +/- 0.5, mean +/- SEM) with a mean fasting urinary calcium to creatinine ration of 0.31 +/- 0.03. Studies described in this report were performed after 1 week of ingesting a diet containing 1,000 mg calcium, 3,000 mg sodium, and 100 mg purine. Clearance of creatinine ranged from 84 to 159 ml/min per 1.73 m2. Tm phosphate (mg/100 ml GFR) was normal in each child (mean 4.66 +/- 0.06 mg/100 ml GFR). Fractional excretion of uric acid, sodium and beta-2-microglobulin were also normal in each child. Serum bicarbonate concentrations ranged from 21.5 to 27 mEq/l with a mean of 24.4 +/- 0.5 mEq/l and all patients lowered urinary pH to less than 5.5. Hypotonic diuresis demonstrated normal free water clearance with a mean of 12.8 ml/min per 100 ml Cin. Distal sodium delivery and fractional distal sodium reabsorption were normal with a mean of 13.6 +/- 1.2% and 92.7 +/- 0.5%, respectively. Water deprivation studies demonstrated a range of maximum urinary osmolality from 711 to 1,020 mosmol/kg H2O with a mean of 864 +/- 34 mosmol/kg H2O. Seven healthy children, ingesting an identical study diet, concentrated their urine to a mean of 1,059 +/- 31 mosmol/kg h2O.(ABSTRACT TRUNCATED AT 250 WORDS)