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Low prevalence of hypercalciuria in Japanese children
Kazunari Kaneko1, Kumi Tsuchiya, Risako Kawamura
1Department of Pediatrics, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. kkaneko@med.juntendo.ac.jp
Insights
Japanese children have a low prevalence of hypercalciuria, with only 0.6% exhibiting high urinary calcium excretion. This finding may explain the lower rates of kidney stones (urolithiasis) in this population.
Area of Science:
- Pediatric Nephrology
- Urology
- Public Health
Background:
- Urolithiasis (kidney stone formation) prevalence varies globally.
- Japanese children exhibit a notably low incidence of urolithiasis, but the underlying reasons are not well understood.
- Urinary calcium excretion is a key factor in kidney stone formation.
Purpose of the Study:
- To investigate the prevalence of hypercalciuria (elevated urinary calcium) in healthy Japanese children.
- To explore the potential link between urinary calcium levels and the low prevalence of urolithiasis in this demographic.
Main Methods:
- A population-based school survey screened 529 healthy Japanese children.
- Hypercalciuria was assessed by measuring the urinary calcium to creatinine (Ca/Cr) ratio in morning fasting urine.
- Urinary sodium to creatinine (Na/Cr) ratio was also calculated for correlation analysis.
Main Results:
- Only 0.6% of children (3/529) showed hypercalciuria (urinary Ca/Cr > 0.17).
- The majority (93.4%) exhibited hypocalciuria (urinary Ca/Cr < 0.05), with a mean Ca/Cr of 0.024.
- A positive correlation was found between urinary Ca/Cr and Na/Cr ratios (rs = 0.14, p < 0.01); no age or sex relation was observed.
Conclusions:
- Japanese children have a significantly lower prevalence of hypercalciuria compared to other populations.
- This low prevalence of hypercalciuria is a potential contributing factor to the reduced incidence of urolithiasis in Japanese children.
- Further research, possibly involving dietary interventions (low calcium/sodium), is recommended to understand urolithiasis prevention in this group.
Background/Aim:
There are several factors, such as race, age, sex, and geographical variations, associated with renal stone formation. Although it is known that the prevalence of urolithiasis in Japanese children is low, the reason remains obscure. We hypothesize that the low prevalence of urolithiasis is associated with the urinary calcium excretion. The aim of our study was to investigate the prevalence of hypercalciuria in Japanese children.
Methods:
This investigation is a population-based school survey. A group of 529 healthy Japanese children was screened for hypercalciuria by measurement of the urinary Ca/Cr ratio using the morning fasting urine. In addition, the urinary Na/Cr ratio was also calculated for each subject.
Results:
Hypercalciuria regarded as an urinary Ca/Cr value of more than 0.17 was noted only in 3 out of 529 children (0.6 %), while most cases (494/529, 93.4%) demonstrated hypocalciuria (urinary Ca/Cr <0.05). The mean urinary Ca/Cr value was 0.024 in all subjects combined. Linear regression analysis revealed a positive direct correlation between urinary Ca/Cr and Na/Cr values (rs = 0.14, p < 0.01). The urinary Ca/Cr ratio was not related to age in either sex.
Conclusions:
The present study demonstrates that the prevalence of hypercalciuria in Japanese children is low as compared with other countries, even though absorptive hypercalciuria and dietary hypercalciuria might be missed in this setting. This low prevalence of hypercalciuria may be associated with the lower prevalence of urolithiasis in Japanese children. As it is suggested that a low dietary intake of calcium and sodium may play some role in the low urinary calcium excretion, a randomized, controlled study comparing the efficacy of different modes of therapy, such as a low-calcium diet and/or a low-salt diet, might provide valuable information for the prevention of urolithiasis.