Bone mineral content, corrected for height or bone area, measured by DXA is not reduced in children with chronic renal disease or in hypoparathyroidism.

The combination of poor growth and parathyroid and mineral disorders complicates the diagnosis of renal bone disease in children with chronic renal insufficiency (CRI), and the role of dual X-ray absorptiometry (DXA) is unclear. We aimed to examine the role of DXA in assessing variation in size-adjusted bone mineral content (BMC) in children with CRI and compare it with a cohort with hypoparathyroidism (HPT) and pseudo-hypoparathyroidism (PHPIa). In 29 patients with CRI (21 male) with a median age of 11 years (10th, 90th centiles 4.4, 14.6) and 10 patients with HPT and PHPIa (three male), with a median age of 13.7 years (7, 16) lumbar spine (LS) and total body (TB) BMC were measured by DXA. Age-, gender- and height-matched data allowed calculation of percentage predicted bone area for age and gender (pBAr) and percentage predicted BMC for bone area and height. In the CRI group, the median glomerular filtration rate (GFR) was 27.4 ml/min per 1.73 m2 (7.1, 69.5), and the median duration of illness was 9.3 years (2.1, 12.1). Median height standard deviation score (Ht SDS) was -1.6 (-3.0, 0.3), and, as expected, median LS and TB pBAr were low at 82% (68, 974) and 76% (63, 92), respectively. LS and TB predicted BMC (pBMC) SDS (corrected for bone size) were generally high, with a median value of 0.4 (-0.9, 1.4) and 0.4 (-0.1,0.9), respectively. Analysis of the prepubertal subset of children (n=15) showed that median percentage predicted LS BMC for height was 104% (80, 116), whereas the median TB BMC for height was 96% (74, 108). Median Ht SDS of the HPT and PHPIa cohort was -0.3 (-2.9, 0.3) and median LS and TB pBAr were 90% (66, 100) and 91% (76, 98), respectively. Median LS and TB pBMC SDS were 0.6 (-0.4, 1.8) and 0.7 (0.3, 1.1), respectively. Median percentage predicted LS and TB BMC for height were 102% (82, 114) and 102% (92, 122). There was no relationship between pBMC SDS and duration of illness, GFR, vitamin D dose, serum intact parathyroid hormone (PTH), serum calcium/phosphate product or serum total alkaline phosphatase (ALP) in the CRI or the HPT cohort. However, one of the highest pBMC SDSs was recorded in a child with PHPIa before she started on any treatment. In children with CRI, BMC, when adjusted for co-existing growth retardation, is similar to that observed in children with hypoparathyroidism. The correct reading of BMC needs a correction for bone size.

Glomerular basement membrane thickness in children: a stereologic assessment.

BACKGROUND: Stereologic methods have emerged as the technique of choice in assessing glomerular basement membrane (GBM) thickness, following conceptual modeling comparing the stereologic technique of harmonic mean of the orthogonal intercept estimation (Th) with the model based method of arithmetic mean estimation (ATH), with no direct comparison undertaken. We undertook to establish the gold standard for GBM estimation and use this technique to establish a range for GBM thickness in children. METHODS: Intra-observer and inter-glomerular variation was estimated in 34 cases with (presumed) normal GBM thickness, using Th, ATH and a rapid direct measurement technique, with intra-observer variation measured in 35 cases with GBM attenuation. A total of 34,011 measurements were undertaken to establish a range for Th in children on 212 biopsies from 199 patients (127 male) demonstrating minimal change nephropathy (N = 153), focal segmental glomerulosclerosis (24), no abnormality (24), and acute tubular necrosis (8), which were used as surrogates for normals. RESULTS: Th demonstrated less variation than ATH in both the normal and attenuated groups. GBM thickness increased throughout childhood, from 194 +/- 6.5 nm (mean +/- SE) at one year to 297 +/- 6.0 nm at 11 years, with a reduced rate of increase after age 11 years. CONCLUSION: Stereologic methods are superior to model based techniques in estimating GBM thickness and should be regarded as the technique of choice in this area. GBM thickness was observed to increase during childhood with no gender effect demonstrable as a main effect or interaction.

Skeletal disproportion in children with chronic renal disease.

OBJECTIVES: To assess stature and skeletal disproportion in children with chronic renal disease. METHODS: Cross-sectional study of height (HT), sitting height (SH), subischial leg length (SILL), sitting height/height ratio (SH:HT) and disproportion score (SH SDS minus SILL SDS) in 56 children (M:35) with median age 11.4 years (range 4.5,18.7) with chronic renal disease. RESULTS: There were 19 children with chronic renal insufficiency, 6 receiving peritoneal dialysis and 31 after renal transplant. The median HTSDS for the whole group was -1.21 (-2.8, 0.35). The median SH:HT ratio in non-transplanted children and renal transplant were 0.51 (0.49, 0.53) and 0.50 (0.48, 0.53), respectively (p = 0.02). The median disproportion score of the whole group was -3.2 (-4.8, -1.8). There was a significant correlation between disproportion score and SH:HT (r = 0.5, p = 0.005). SH:HT ratio was negatively related to duration of illness (r = 0.4, p = 0.005). CONCLUSION: Children with chronic renal disease have significant body disproportion and this may be due to a disproportionately greater effect of disease and treatment on spinal growth.