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Renal potassium excretion is reduced in children with idiopathic hypercalciuria
J Rodríguez-Soriano1, M Ubetagoyena, A Vallo
1Department of Pediatrics, Hospital Infantil de Cruces, Bilbao, Spain.
Insights
Children with idiopathic hypercalciuria show decreased renal potassium excretion. Elevated urinary calcium levels in these children are linked to reduced potassium secretion, suggesting a similar effect in humans as observed in rats.
Area of Science:
- Nephrology
- Pediatric Nephrology
- Renal Physiology
Background:
- Elevated luminal calcium in the distal tubule is known to inhibit potassium secretion in rats.
- The in vivo effect of increased luminal calcium on renal potassium excretion in humans, particularly in children, remains less understood.
Purpose of the Study:
- To investigate the relationship between urinary calcium excretion and renal potassium excretion in children.
- To determine if hypercalciuria in children is associated with altered potassium handling by the kidneys.
Main Methods:
- Cross-sectional study comparing renal electrolyte excretion in children with idiopathic hypercalciuria and age-matched controls.
- Measurement of urinary calcium, sodium, and potassium excretion, including fractional excretion and transtubular potassium concentration gradient.
- Assessment of changes in these parameters following an oral calcium load in a subset of hypercalciuric children.
Main Results:
- Children with idiopathic hypercalciuria exhibited significantly higher sodium excretion and lower fractional potassium excretion compared to controls.
- All indices of potassium excretion were inversely correlated with urinary calcium excretion.
- An oral calcium load in hypercalciuric children led to increased sodium excretion and a decreased transtubular potassium concentration gradient.
Conclusions:
- Increased urinary calcium concentration is associated with reduced renal potassium secretion in children.
- Findings support the hypothesis that elevated luminal calcium inhibits renal potassium secretion in humans.
- This study highlights a potential mechanism linking hypercalciuria to altered potassium balance in pediatric populations.
Abstract:
Increased luminal calcium decreases potassium secretion in microperfused rat distal tubule. To determine if such an effect is also present in vivo, we evaluated renal potassium excretion in 49 children with idiopathic hypercalciuria (urinary excretion of Ca = 5.5 +/- 1.3 mg/kg/day) and in 214 age-matched control children (urinary excretion of Ca = 1.9 +/- 0.3 mg/kg/day). In comparison to controls, hypercalciuric children had significantly increased levels of sodium excretion (fractional excretion of Na = 0.7 +/- 0.3 vs. 0.6 +/- 0.3%, respectively; p less than 0.001) and decreased levels of fractional potassium excretion (7.2 +/- 2.9 vs. 9.2 +/- 3.4%, respectively; p less than 0.001) and of the transtubular potassium concentration gradient (4.2 +/- 1.5 vs. 5.9 +/- 1.5, respectively; p less than 0.001). All indices of potassium excretion correlated significantly and inversely with urinary calcium excretion (p less than 0.001). After an oral calcium load, performed in 30 hypercalciuric children, the increased rates of urinary calcium excretion were accompanied by increased rates of urinary sodium excretion and by a significant decrease in the transtubular potassium concentration gradient. These results support the hypothesis that increased luminal calcium concentration also inhibits renal potassium secretion in man.