Spontaneous urinary calcium oxalate crystallization in hypercalciuric children

Biochemical metabolic levels and vitamin D receptor FokⅠ gene polymorphisms in Uyghur children with urolithiasis

Because of lacking studies of urolithiasis in children, we detected the biochemical metabolic levels and FokⅠ polymorphisms in the vitamin D receptor (VDR) in Uyghur children with urolithiasis, and evaluated the associations of biochemical metabolic levels with FokⅠ genotypes. We included 142 Uyghur children (108 males) under age 14 years with a diagnosis of urolithiasis and 238 Uyghur children (154 males) under age 14 years without a history of urolithiasis as controls. Baseline information and data for serum and urine parameters were obtained from medical records. PCR-restriction fragment length polymorphism (PCR-RFLP) was used to analyze the VDR FokⅠ polymorphisms. In univariate analyses adjusting for age and sex, carbon dioxide combining power (CO2CP) (odds ratio [OR] = 1.13, 95% confidence interval [CI]: 1.07-1.19), serum magnesium (Mg) (OR = 1.27, 95% CI: 1.03-1.56) and serum chlorine (Cl) (OR = 0.93, 95% CI: 0.88-0.97) were related to Uyghur children urolithiasis risk. A multiple logistic regression model showed CO2CP (OR = 1.17, 95% CI: 1.09-1.26), levels of uric acid (OR = 1.01, 95% CI: 1.00-1.01) and serum sodium (Na) (OR = 0.90, 95% CI: 0.82-0.99) were associated with pediatric urolithiasis. The risk of urolithiasis was increased with the F versus f allele overall (OR = 1.42; 95% CI: 1.01-2.00) and for males (OR = 1.52, 95% CI: 1.02-2.27). However, metabolic levels did not differ by FokⅠ genotypes. In our population, CO2CP and levels of uric acid and serum Na as well as polymorphism of the F allele of the VDR FokⅠ may provide important clues to evaluate the risk of urolithiasis in Uyghur children.

Factors Associated With the Lower Prevalence of Nephrolithiasis in Children Compared With Adults

OBJECTIVE

To determine the reasons behind the lower prevalence of kidney stones in children by assessing urinary lithogenic parameters in healthy children, healthy adults, and 3 groups of stone-former patients.

METHODS

The study subjects included 75 healthy adults, 105 healthy children, 62 patients with previous calcium oxalate monohydrate papillary stones, 120 patients with previous calcium oxalate monohydrate unattached stones, and 248 patients with previous calcium oxalate dihydrate stones. Twenty-four-hour urine samples were collected, and the urinary lithogenic parameters were measured.

RESULTS

Calcium, magnesium, and phosphorous concentration differed significantly between healthy children and adults. Except citrate, all solute/creatinine ratios differed between healthy children and adults. However, these differences were much more important in the cases of calcium and magnesium. The calcium/creatinine ratio was 2-fold lower, whereas the magnesium/creatinine ratio was 2-fold higher, in healthy children than that in healthy adults (P <.001 each). The calcium/creatinine ratio was higher and the citrate/creatinine ratio lower in calcium oxalate dihydrate stone formers than that in healthy adults.

CONCLUSION

Ratios of calcium and magnesium to creatinine, as well as morphoanatomic factors and lifestyle habits, may explain the lower prevalence of nephrolithiasis in children than those in adults.