Analysis of urinary parameters as risk factors for nephrolithiasis in children with celiac disease.

PURPOSE: Intestinal malabsorption can cause urinary stone disease via enteric hyperoxaluria. It has been shown that celiac disease, a common malabsorption disorder, is associated with an increased risk of calcium oxalate kidney stones in adults. Since no published data are available in the pediatric population, we analyzed urinary excretion of electrolytes in children with celiac disease to assess the risk of nephrolithiasis. MATERIALS AND METHODS: The study population consisted of 115 children 1 to 16 years old (mean 5 years) with positive serological tests for celiac disease (anti-endomysium and anti-tissue transglutaminase antibodies) referred to us for jejunal biopsy to confirm the diagnosis. Assessment was requested because patients presented with poor growth, anemia, gastrointestinal disorders or a family history of celiac disease. After obtaining informed consent we performed urine tests to measure urinary variables and blood tests to exclude metabolic disorders and evaluate renal function. RESULTS: All patients had a biopsy confirmed diagnosis of celiac disease. Oxaluria was normal in all children studied. However, levels of urinary calcium were decreased in patients with celiac disease and were inversely associated with disease severity (p = 0.0004). CONCLUSIONS: In contrast to adults, increased urinary excretion of oxalate was not detectable in children presenting with celiac disease. Therefore, the risk of nephrolithiasis appears not to be increased compared to healthy children. The observed hypocalciuria probably further decreases the tendency to form kidney stones.

Reference values of the bioelectrical impedance vector in neonates in the first week after birth.

OBJECTIVE: To determine the reference, bivariate, tolerance intervals of the whole-body impedance vector for healthy white neonates, we performed an observational, cross-sectional study in two university hospitals. METHODS: The impedance vector (standard, tetrapolar analysis at 50-kHz frequency) was measured in 163 consecutive subjects (87 boys and 76 girls) with postnatal ages of 1 to 7 d. Bivariate vector analysis was conducted with the resistance-reactance (RXc) graph method. RESULTS: The age-specific 95% confidence intervals of mean vectors and the 95%, 75%, and 50% tolerance intervals for individual vector measurements were plotted using R and Xc components standardized by the subject's crown-to-heel length (height). Mean vectors from the groups (1, 2, and 3 to 7 d) with overlapping 95% confidence ellipses were considered representative of only one age class of 1 to 7 d. The impedance vector distribution of neonates also was compared with healthy white children (1014 boys and 1030 girls, age 2-15 y) and adult subjects (354 men and 372 women, age 15-85 y) from the same geographic area. There was a definite, progressive, vector shortening from birth, through ages 2 to 15 y, toward the adults' vector position. CONCLUSIONS: We established the reference, bivariate, 95%, 75%, and 50% tolerance intervals of the impedance vector in the first postnatal week for healthy white neonates, with which the vectors from infants with altered body composition can be tested (free software is available from apiccoli@ unipd.it).

"Bartter-like" phenotype in Kearns-Sayre syndrome.

Kearns-Sayre syndrome (KSS) is a mitochondrial disease caused by large deletions in mitochondrial DNA (mtDNA). In most patients the disease is characterized by mtDNA heteroplasmy, where a mixture of wild-type and mutated mtDNA co-exist within cells in variable proportion, modulating the severity of the phenotype in different tissues. We report on the case of a 14-year-old child with classical symptoms of KSS and a renal phenotype characterized by hypokalaemic alkalosis, hypomagnesaemia, hyperreninaemia, hyperaldosteronism and nephrocalcinosis, resembling Bartter syndrome. Analysis of mtDNA demonstrated an 8,661 bp deletion involving eight mitochondrial genes. Uneven degrees of mtDNA heteroplasmy were demonstrated in several tissues, ranging from 24% to 60% of deleted/total mtDNA. Variable degrees of expression of mitochondrial enzymes were also found in biopsy specimens of renal and skeletal muscle by histocytochemistry. In particular, preserved cytochrome c oxidase was observed in tubular structures within medullary rays. It is proposed that a "Bartter-like" phenotype can arise in some patients with KSS as a result of heteroplasmy. In these cases aldosterone-responsive tubular structures have been spared during renal embryogenesis, allowing for the development of hypokalaemic alkalosis in response to salt and water losses from the more damaged tubular segments.

Predictive value of amniotic fluid cystatin C levels for the early identification of fetuses with obstructive uropathies.

OBJECTIVE: To compare the diagnostic accuracy of cystatin C with that of creatinine in discriminating renal function in fetuses without ultrasononographic evidence of renal malformations from those with obstructive uropathies. DESIGN: Prospective, observational cohort study. SETTING: Prenatal morphologic and functional evaluation of fetal obstructive uropathies throughout pregnancy. POPULATION: A total of 96 healthy pregnant women at different stages of pregnancy, without any pregnancy-related maternal disease. Eighty-one pregnant women without clinical and ultrasonographic evidence of any fetal anomaly, confirmed at birth, were defined as controls; 15 pregnant women with various fetal obstructive uropathies, evidenced by repeated ultrasound examinations and confirmed at birth, were defined as cases. METHODS: Creatinine was measured by a kinetic Jaffe picric acid method and cystatin C by a nephelometric immunoassay. Variables were analysed by applying conventional statistical tests; the non-parametric receiver operating curves (ROC) analysis was used to evaluate the diagnostic efficiencies of the biochemical markers. MAIN OUTCOME MEASURES: Incidence of confirmed, diagnosed, neonatal obstructive uropathy by measuring baseline levels of cystatin C and creatinine in amniotic fluid. RESULTS: Baseline levels of cystatin C in amniotic fluid were significantly higher (P = 0.0015) among cases than in controls with comparable gestational age; no significant difference was found for creatinine levels (P = n.s.). The maximum diagnostic accuracy of serum cystatin C in discriminating controls from fetal uropathies was 96%, while that of creatinine was 62%. CONCLUSION: Cystatin C may be considered a sensitivebiochemical marker for the early identification of fetuses with obstructive uropathies.