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Hypercalciuria in children with juvenile rheumatoid arthritis: association with hematuria
Insights
Juvenile rheumatoid arthritis (JRA) patients frequently show increased urinary calcium excretion (hypercalciuria). This condition may contribute to hematuria in some children with JRA.
Area of Science:
- Pediatric Rheumatology
- Nephrology
- Metabolic Bone Disease
Background:
- Juvenile rheumatoid arthritis (JRA) is a chronic inflammatory condition affecting children.
- Hematuria and urolithiasis are potential complications that warrant further investigation into underlying metabolic factors.
- Hypercalciuria, elevated urinary calcium levels, is a condition that can predispose to kidney stones and other urinary tract issues.
Observation:
- Urinary calcium/creatinine (UCa/UCr) ratios were assessed in 38 pediatric patients with JRA.
- Increased fasting UCa/UCr ratios were identified in 12 patients (31.6%), significantly higher than in normocalciuric controls.
- Higher prevalence of elevated UCa/UCr ratios was noted in patients with systemic JRA.
Findings:
- Four patients with elevated UCa/UCr underwent further testing, confirming fasting hypercalciuria even after dietary calcium restriction.
- Serum calcium, phosphorus, and parathyroid hormone levels were within normal ranges in all tested patients.
- Hematuria occurred more frequently in hypercalciuric JRA patients (6/12) compared to normocalciuric patients (3/26).
Implications:
- Urinary calcium excretion is frequently elevated in children with JRA.
- Hypercalciuria may play a role in the development of hematuria in some pediatric JRA patients.
- Further research is needed to elucidate the mechanisms linking JRA, hypercalciuria, and urinary tract complications.
Abstract:
After discovering juvenile rheumatoid arthritis (JRA), hematuria, and urolithiasis associated with hypercalciuria in two children, urinary calcium excretion was examined in 38 patients with JRA. Fasting urine calcium/creatinine (mg/mg) (UCa/UCr) ratios were increased (greater than 0.21) in 12 patients, who had a mean UCa/UCr ratio of 0.34 +/- 0.14, compared with 0.09 +/- 0.06 in 26 normocalciuric patients with JRA. Increased UCa/UCr ratios were found more frequently in patients with systemic JRA (P less than 0.05); however, no relationship between UCa/UCr ratios and either functional classification or drug therapy was observed. Four children with increased urine calcium to creatinine ratios were examined more extensively. Twenty-four-hour urine calcium excretion ranged from 4.0 to 7.2 mg/kg/24 hours. An orally administered calcium loading test demonstrated fasting hypercalciuria after dietary calcium restriction in these four patients. Serum calcium, bicarbonate, phosphorus, and parathyroid hormone values were normal. Hematuria was found in six of 12 hypercalciuric patients with JRA but in only three of 26 normocalciuric patients (P less than 0.016). We conclude that urinary calcium excretion is frequently increased in patients with JRA and that hypercalciuria may be related to the pathogenesis of hematuria in some of them.