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Screening for hypercalciuria
1Division of Nephrology, Saitama Children's Medical Center, Japan.
Insights
Establishing reference values for urinary calcium/creatinine (Ca/Cr) ratio in children provides a screening tool for elevated calcium excretion. This study subclassified idiopathic hypercalciuria, suggesting disordered vitamin D metabolism in absorptive hypercalciuria.
Area of Science:
- Pediatric Nephrology
- Clinical Biochemistry
- Metabolic Bone Disease
Background:
- Idiopathic hypercalciuria (IH) is a common condition in children with unclear pathogenesis.
- Accurate reference values for urinary calcium excretion are crucial for diagnosis and management.
- The urinary calcium/creatinine (Ca/Cr) ratio is a widely used index for assessing calcium excretion.
Purpose of the Study:
- To establish reference values for the urinary Ca/Cr ratio in healthy children.
- To investigate the relationship between Ca/Cr ratio, age, and sex.
- To subclassify idiopathic hypercalciuria based on urinary Ca/Cr ratios and calciuric response.
Main Methods:
- Cross-sectional study of 361 healthy children aged 5-15 years.
- Measurement of urinary Ca/Cr ratio in first morning voided urine on unrestricted diets.
- Assessment of calciuric response to calcium-restricted diets and oral calcium loading tests.
Main Results:
- Urinary Ca/Cr ratio was independent of sex but dependent on age.
- The first morning urinary Ca/Cr ratio on unrestricted diets served as a reliable screening test for elevated calcium excretion.
- IH was subclassified into absorptive, renal, and dietary hypercalciuria.
- Disordered 1,25(OH)2 vitamin D metabolism with excessive urinary phosphate excretion was suggested in absorptive hypercalciuria.
Conclusions:
- Reference values for urinary Ca/Cr ratio in children are established.
- First morning urinary Ca/Cr ratio is a valuable screening tool for hypercalciuria.
- Subclassification of IH aids in understanding its diverse pathophysiology.
- Abnormal vitamin D metabolism may contribute to absorptive hypercalciuria.
Abstract:
Reference values for the urinary calcium/creatinine ratio (Ca/Cr ratio) in the first morning urine were established in 361 healthy children aged 5 to 15 years, on unrestricted diets. The urinary Ca/Cr ratio in the urine upon arising was independent of sex but dependent upon age. The measurement of the urinary Ca/Cr ratio in the urine upon arising while on unrestricted diets may be a reasonable screening test for elevated calcium excretion. On the basis of the urinary Ca/Cr ratios in the urine upon arising during unrestricted diets and the calciuric response to calcium restricted diets and the oral calcium loading test, idiopathic hypercalciuria (IH) was subclassified into three groups: (1) absorptive hypercalciuria; (2) renal hypercalciuria; (3) dietary hypercalciuria. The pathogenesis of IH is controversial. Our data suggest that disordered 1,25 (OH)2 vitamin D metabolism with excessive urinary phosphate excretion occurs in absorptive hypercalciuria.