Low Prevalence of Hypercalciuria in Japanese Children

Abstract

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.

Prevalence of hypercalciuria and urinary calcium excretion in school-aged children in the province of Tokat

“…In Japan, the prevalence of hypercalciuria was only 0.6% in 529 school-age children, though the limit value for UCa/ Cr was considered 0.17 (18). It was thought that this low prevalence of hypercalciuria was related with low calcium and dietary salt intake, and this could be one of the causes of the low incidence of urolithiasis in Japan (18).…”

“…It was thought that this low prevalence of hypercalciuria was related with low calcium and dietary salt intake, and this could be one of the causes of the low incidence of urolithiasis in Japan (18). In a study conducted with children aged between 5 and 12 years in India, the prevalence of hypercalciuria was 6.5% (19).…”

Idiopathic hypercalciuria in children with urinary tract infection

“…15 For example, in Eastern Europe countries, IH prevalence ranges between 3% and 7%; while in other countries it is as follows: Spain: 3.8%, Germany: 8.6%, Italy: 9.1%; United States of America: 10%, Japan: 0.6%, and Brazil: 3.2%. 6,9,15,18,[26][27][28][29] Moreover, such variability has been observed among different regions in the same country. For example, four Iranian studies reported that IH prevalence was 0.2%, 3.6%, 11.4%, and 13.3%, respectively.…”

“…Based on this, it is possible to infer that IH rate among children 6 6 included in our study is higher than in the general population. 6,9,15,18,[26][27][28][29] Besides, IH prevalence in children with VUR had been previously studied because VUR prevalence among children with kidney stones (4%-8%) 31 is higher than in the healthy population (<1%) 32 . García Nieto described a very high rate (58.6%) of IH compared to the general population of his country.…”

“…However, IH prevalence among our patients is clearly higher than that described for asymptomatic children worldwide. [6][7][8][9][10]15,[26][27][28][29] Also, in contrast to previous studies, 12,35 the prevalence of a family history of lithiasis in patients with hypercalciuria was extremely uncommon. This may be due to the fact that search was restricted to first-degree relatives; still, 20% of patients reported that they were unaware of such information.…”