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Renal and absorptive hypercalciuria: a metabolic disturbance with varying and interchanging modes of expression
1Department of Pediatrics, Assaf Harofeh Medical Center, Zerifin, Israel.
Insights
Idiopathic hypercalciuria in children may not have distinct subtypes. Sodium intake appears to be the primary factor influencing calcium excretion, suggesting a continuum rather than separate conditions.
Area of Science:
- Pediatric Nephrology
- Mineral Metabolism
- Urolithiasis Research
Background:
- Idiopathic hypercalciuria (IH) in children is often classified using oral calcium loading and deprivation tests.
- Distinguishing between renal hypercalciuria (RH) and absorptive hypercalciuria (AH) has been a focus in previous research.
Purpose of the Study:
- To evaluate the long-term clinical course of children diagnosed with idiopathic hypercalciuria.
- To investigate the impact of urinary sodium excretion on urinary calcium excretion in these children.
Main Methods:
- Thirty children with idiopathic hypercalciuria were assessed.
- Patients were categorized into absorptive hypercalciuria (AH) and renal hypercalciuria (RH) groups based on response to calcium tests.
- Urinary sodium and calcium excretion were measured over a 3-7 year follow-up period.
Main Results:
- A significant proportion of children shifted between AH and RH classifications over time.
- A positive correlation was found between urinary sodium and calcium excretion in both AH and RH groups.
- Lower urinary sodium excretion was associated with normocalciuria at follow-up.
Conclusions:
- The distinction between AH and RH in children may be artificial, suggesting a continuum of the condition.
- Urinary calcium excretion in children with idiopathic hypercalciuria appears to be significantly influenced by sodium intake.
- Long-term follow-up reveals dynamic changes in hypercalciuria subtypes.
Background:
In previous studies, the oral calcium loading and deprivation test has been used to distinguish between children with renal (fasting) hypercalciuria (RH) and absorptive hypercalciuria (AH).
Objective:
We evaluated the long-term clinical course of 30 children with idiopathic hypercalciuria and investigated the influence of urinary sodium excretion, as a reflection of its intake, on urinary calcium excretion.
Methods:
Thirty normocalcemic, normophosphatemic children (21 boys and 9 girls) with urinary calcium to creatinine ratios greater than 0.57 mmol/L/mmol/L ( > 0.21 mg/dL/mg/dL on the three consecutive examinations participated in this study. They were divided according to their responses to calcium deprivation and loading into AH (16 patients) and RH (14 patients).
Results:
When restudied 3 to 7 years later, 6 of the 16 children with AH were normocalciuric and three demonstrated characteristics compatible with RH. The remaining seven patients maintained their initial AH pattern. Of the 14 children with RH, four were normocalciuric and four demonstrated AH. The remaining six children maintained their initial RH pattern. A significant positive correlation was observed between urine sodium and calcium excretion in children with AH or RH. Children who were normocalciuric at the second study had significantly lower values of urine sodium excretion when compared with those in whom hypercalciuria persisted.
Conclusions:
We suggest that AH and RH constitute a continuum. The change in characteristics observed during the second study suggests that any attempt to divide these patients into two physiologically distinct subtypes may be artificial. The main factor influencing urinary excretion of calcium in our patients seemed to be sodium intake.