Bone Abstracts

Objective: Idiopathic hypercalciuria (IH) is defined as excessive 24 h urinary calcium excretion (>4 mg/kg per 24 h), that persists after correction of dietary imbalances in the absence of secondary causes. Recent studies with DXA in children with IH provide evidence of decreased areal BMD. We used peripheral quantitative computed tomography (pQCT) of the tibia, to test the hypothesis that IH results in decreases of volumetric (mg/cm³) BMD of the trabecular and/or cortical compartment of bone.

Patients and methods: We studied 14 children (eight boys and six girls, aged 6–18 years) with newly discovered IH that were admitted to our clinic. Most of them presented with either hematuria or recurrent abdominal or lumbar pain. After establishment of the diagnosis, all children underwent DXA of the lumbar spine. We also performed pQCT of the tibia (Stratec XCT-2000 scanner), 4 slices were obtained at the 4, 14, 38 and 66% of tibia length sites. For the 4% slice, we assessed variables of trabecular bone and especially trabecular BMD (TRAB_DEN, mg/cm³). For 14% we assessed parameters of subcortical bone and for the 38 and 66% sites parameters of cortical bone. pQCT data of the children with IH were compared to those of healthy race-, age- and sex-matched children from the published pQCT database of Moyer–Miller et al. (J Clin Densitom 2008) who used the same pQCT device, software, and site measurements that we did.

Results: 7/14 children with IH (50%) were found to have Z-scores<−1 S.D. in the DXA measurements of the lumbar spine. For the pQCT measurements, we report here only the preliminary results of trabecular BMD (ongoing analysis). 8/14 children with IH (57%) had reduced volumetric bone mineral density (TRAB_DEN<2 S.D.) when compared with healthy children of the same age, race, sex and height of the Moyer-Miller study.

Conclusion: Our study provides preliminary evidence of reduced trabecular bone mineral density in children with IH as compared to healthy ones.