Urinary volume in children with urolithiasis

How to Monitor Hydration Status and Urine Dilution in Patients with Nephrolithiasis

Maintenance of hydration status requires a tight balance between fluid input and output. An increase in water loss or a decrease in fluid intake is responsible for dehydration status, leading to kidney water reabsorption. Thus, urine volume decreases and concentration of the different solutes increases. Urine dilution is the main recommendation to prevent kidney stone recurrence. Monitoring hydration status and urine dilution is key to preventing stone recurrence. This monitoring could either be performed via spot urine or 24 h urine collection with corresponding interpretation criteria. In laboratory conditions, urine osmolality measurement is the best tool to evaluate urine dilution, with less interference than urine-specific gravity measurement. However, this evaluation is only available during time lab examination. To improve urine dilution in nephrolithiasis patients in daily life, such monitoring should also be available at home. Urine color is of poor interest, but reagent strips with urine-specific gravity estimation are currently the only available tool, even with well-known interferences. Finally, at home, fluid intake monitoring could be an alternative to urine dilution monitoring. Eventually, the use of a connected device seems to be the most promising solution.

Dietary management of hypocitraturia in children with urolithiasis: results from a systematic review

PURPOSE

Hypocitraturia is a low urinary excretion of citrate and a well-known risk factor for kidney stone development in children. This systematic review aimed to evaluate the dietary management of hypocitraturia in children with urolithiasis.

METHODS

Literature search was performed on 30th September 2022 using Embase, PubMed, and Cochrane Central Controlled Register of Trials. Studies were included if children with stones and hypocitraturia were managed with diet supplements.

RESULTS

Six papers were included. Four studies evaluated the role of oral potassium citrate associated with high fluid intake on stone resolution and recurrence. Two studies assessed the impact of oral potassium citrate on long-term stone recurrence after percutaneous nephrolithotomy and shock wave lithotripsy. All studies demonstrated that the association of potassium citrate and high fluid intake was well tolerated with no side effects and restored normal urine citrate excretion, allowed a reduction in stone size, and, following definitive treatments, was associated with a lower rate of stone regrowth and recurrence compared with controls. These effects were demonstrated across all pediatric ages.

CONCLUSIONS

Our review infers that oral potassium citrate and high fluid assumption are safe and effective in restoring urine citrate excretion, treating and preventing stone recurrence with no serious adverse events, and should probably be the first-line treatment of pediatric patients with asymptomatic stones and hypocitraturia.

Association between fluoroquinolone exposure and children's growth and development: A multisite biomonitoring-based study in northern China

BACKGROUND

Although animal experiments found that antibiotic exposure during early life increased adiposity, limited human epidemiological evidence is available for the effects of veterinary antibiotic exposure on children's growth and development.

OBJECTIVE

This study was conducted to examine the body burden of fluoroquinolones in northern Chinese children and assess its association with growth and development.

METHODS

After recruiting 233 children aged 0-15 years from 12 different sites in northern China in 2020, we measured urinary concentrations of 5 respective fluoroquinolones (fleroxacin, ofloxacin, norfloxacin, ciprofloxacin, and enrofloxacin) by high performance liquid chromatography. Categories of children's growth and development were identified based on the Z score of body mass index. The health risks of individual and combined antibiotic exposure were estimated by the hazard quotient (HQ) and hazard index (HI), respectively. The association between children's growth and development with antibiotic concentrations was evaluated via multiple logistic regression analysis.

RESULTS

In total, 4 antibiotics, fleroxacin, ofloxacin, ciprofloxacin, and enrofloxacin, were found in urine samples of northern Chinese children at an overall frequency of 57.08%. Due to diet and economic differences, antibiotic concentrations in urine samples differed by study area, and the highest concentrations were found in Tianjin, Henan, and Beijing. The percentage of the participants with HQ > 1 caused by ciprofloxacin exposure was 20.61%, and the HI values in 23.18% of samples exceeded 1, suggesting potential health risks. The odds ratio (95% confidence interval) of overweight or obesity risk of tertile 2 of enrofloxacin was 3.01 (1.12, 8.11), indicating an increase in overweight or obesity risk for children with middle-concentration enrofloxacin exposure.

CONCLUSION

This is the first study to show a positive association of enrofloxacin internal exposure with overweight or obesity risk in children, demonstrating that more attention should be given to the usage and disposal of fluoroquinolones to safeguard children's health.

The Impact of Water and Other Fluids on Pediatric Nephrolithiasis

Pediatric nephrolithiasis cases have been on the rise in the past several years, resulting in increased healthcare costs and other burdens on the juveniles with this ailment. Recent research has shown that present trends in pediatric nephrolithiasis have changed as a result of fluid intake, including water consumption, nutrition, obesity prevalence, lifestyle, and imaging procedures. A specific cause, meanwhile, is still elusive. Trends in pediatric nephrolithiasis need to be thoroughly researched. Furthermore, variables specific to pediatric nephrolithiasis that could cause greater difficulties in an affected child elevate the level of worry with cumulative prevalence. Doctors should rigorously assess patients who present with kidney stones when they have dynamics such as varied clinical presentation, high recurrence of kidney stones linked to metabolic and urinary tract problems, and the potential existence of rare genetic kidney stone illnesses. This review aims to identify adaptive risk factors and anomalies that call for specialized treatment and prescription. More specifically, the major goals of medical and surgical treatments are to eliminate kidney stone risk and stop relapse while concurrently lowering interventional barriers. A dedicated nephrolithiasis clinic run by a pediatric nephrologist, nutritionist, urologist, and clinical nurse may sometimes be beneficial for patients in serious danger. Such a clinic offers significant chances to learn more about pediatric nephrolithiasis, which has been linked to water consumption and hence fosters urgently required study in this area.

Risk Assessment of Dietary Exposure to Organophosphorus Flame Retardants in Children by Using HBM-Data

Due to their extensive usage, organophosphorus flame retardants (OPFRs) have been detected in humans and in the environment. Human are exposed to OPFRs via inhalation of indoor air, dust uptake or dietary uptake through contaminated food and drinking water. Only recently, few studies addressing dietary exposure to OPFRs were published. In this study, we used human biomonitoring (HBM) data of OPFRs to estimate how much the dietary intake may contribute to the total exposure. We estimated by reverse dosimetry, the daily intake of tris (2-chloroethyl) phosphate (TCEP), tris (1-chloro-2-propyl) phosphate (TCIPP), tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) for children using HBM data from studies with sampling sites in Belgium, Denmark, France, Germany, Slovenia and Slovakia. For estimating the dietary exposure, a deterministic approach was chosen. The occurrence data of selected food categories were used from a published Belgium food basket study. Since the occurrence data were left-censored, the Lower bound (LB)—Upper bound (UB) approach was used. The estimated daily intake (EDI) calculated on the basis of urine metabolite concentrations ranged from 0.03 to 0.18 µg/kg bw/d for TDCIPP, from 0.05 to 0.17 µg/kg bw/d for TCIPP and from 0.02 to 0.2 µg/kg bw/d for TCEP. Based on national food consumption data and occurrence data, the estimated dietary intake for TDCIPP ranged from 0.005 to 0.09 µg/kg bw/d, for TCIPP ranged from 0.037 to 0.2 µg/kg bw/d and for TCEP ranged from 0.007 to 0.018 µg/kg bw/d (summarized for all countries). The estimated dietary intake of TDCIPP contributes 11–173% to the EDI, depending on country and LB-UB scenario. The estimated dietary uptake of TCIPP was in all calculations, except in Belgium and France, above 100%. In the case of TCEP, it is assumed that the dietary intake ranges from 6 to 57%. The EDI and the estimated dietary intake contribute less than 3% to the reference dose (RfD). Therefore, the estimated exposure to OPFRs indicates a minimal health risk based on the current knowledge of available exposure, kinetic and toxicity data. We were able to show that the dietary exposure can have an impact on the general exposure based on our underlying exposure scenarios.

Nephrolithiasis: Approach to Diagnosis and Management

Although kidney stones are less common in children than in adults, incidence in children is rising. Kidney stones may lead to significant morbidity in addition to escalating medical costs. Clinical presentation is variable. Bilateral kidney stones in a younger child should prompt work-up for primary hyperoxaluria. Metabolic abnormalities are more frequent in children and can result in frequent stone recurrence. Whole exome sequencing data shows genetic defects in about 30% of stone formers. 24 h urine collection should be conducted when patient receives his usual diet and fluid intake with normal activity. Infrared spectroscopy and X-ray diffraction are used for stone analysis. Urine studies should be delayed by 4-6 wk after stone fragmentation or treatment of any stone related complications. The goal of evaluation is to identify modifiable risk factors for which targeted therapy may be instituted. Primary indications for surgical intervention include pain, infection and obstruction. Extracorporeal shockwave lithotripsy (ESWL), ureteroscopy, and percutaneous nephrolithotomy (PCNL) are most commonly used, and selection is based on stone size, anatomy, composition and anatomy. Advances in technology have allowed a shift to minimally invasive surgeries. Comprehensive management requires multidisciplinary team. Children with kidney stones require long term follow-up with periodic assessment of stone forming activity and ascertaining stone burden. High index of suspicion should be there to diagnose diseases like primary hyperoxaluria, Dent's disease, renal tubular acidosis (RTA) etc. as these diseases have ramifications on kidney function and growth.

Educational review: role of the pediatric nephrologists in the work-up and management of kidney stones

BACKGROUND

The incidence of nephrolithiasis in children and adolescents is increasing and appears to double every 10 years. The most important role of the pediatric nephrologist is to diagnose and modify various metabolic and non-metabolic risk factors, as well as prevent long-term complications especially in the case of recurrent nephrolithiasis.

OBJECTIVE

The purpose of this review is to summarize the existing literature on the etiology and management of pediatric nephrolithiasis.

RESULTS

The incidence of kidney stones is increasing; dietary and environmental factors are probably the main causes for this increased incidence. In most pediatric patients, the etiology for the kidney stones can be identified. Metabolic factors, such as hypercalciuria and hypocitraturia, urinary tract infection, and urinary stasis, constitute leading causes. Herein, we review the etiologies, diagnostic work-up, and treatment options for the most prevalent causes of kidney stones. The detrimental effects of excessive dietary sodium, reduced fluid intake, and the benefits of plant-based over animal-based protein consumption on urinary crystal formation are discussed. We also review the long-term complications.

CONCLUSIONS

Pediatric nephrologists have an important role in the diagnostic work-up and prevention of recurring nephrolithiasis.

Estimation of urine volume in municipal sewage originating from patients receiving antibiotics at a private clinic in Crete, Greece

This study presents an estimation of the urine volume in the wastewater from a real, private clinic in Crete, Greece, during a seven-month period (01/06/2018 to 31/12/2018). Separate estimates were obtained for the volume of urine belonging to patients receiving antibiotics. It was found that the clinic disposed into the local municipal sewage network on the average 3,263 L/month of urine, from which 1,331 L/month (40.8%) belonged to patients receiving antibiotics. According to the pharmacy department of the private clinic, during the period of the study, the most frequently administered groups of antibiotics were on the average 779 g/month cephalosporins (68.1%), 108 g/month fluoroquinolones (9.5%) and others (11.2%), with various active substances including cefuroxime, ciprofloxacin, metronidazole and doxycycline. These active substances act like pollutants when disposed via the municipal sewer network into the environment.

Comparison of Risk Factors for Pediatric Kidney Stone Formation: The Effects of Sex

Background: Urinary stones are affecting more children, and pediatric stone formers have unique pathophysiology compared to adults. While adult stone formers are most frequently male, children have an age dependent sex prevalence. Under 10 years, a majority of stone formers are boys; adolescent stone formers are mostly female. Previous adult studies have shown that stone composition is influenced by the sex and age of the stone former. Thus, we hypothesize that female and male stone forming children will also have sex and age specific stone phenotypes. Methods: Retrospective chart review of a large pediatric center's stone forming children 6/1/2009 to 6/1/2016. Patients were identified by ICD 9 codes: N20, N20.1, and N20.9. Charts were reviewed for radiographic evidence of stones or documented visualized stone passage. Results: One hundred and thirty six subjects: 54 males and 82 females. Females were older, median age 14 years [interquartile range (IQR): 11, 15] vs. males' median age 12 years (IQR: 11, 14) (p < 0.01). Females had lower height z-scores, median 0.2 (IQR: -0.8, 0.8) vs. males' median 0.8 (IQR: -0.2, 1.8) (p < 0.01). Presenting symptoms were similar except flank pain affecting 39% of females vs. 22% of males (p = 0.04). Leukocyte esterase was positive in more females than males (33 vs. 4%) (p < 0.001). Males had a higher BUN/Cr ratio, mean ± standard deviation of 19.8 ± 6.3 vs. 16.6 ± 6.5 in females (p = 0.01). Glomerular hyperfiltration was present in 9% of patients while 35% of patients had estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73 m². Treatment strategies and clinical course were similar except females were told to increase dietary citrate more frequently than males (21 vs. 4%) (p < 0.01). Conclusion: We have provided a novel analysis and demonstrated that low height z-score and pyuria are more common in female stone formers. We have also shown that 9% of pediatric stone formers have labs consistent with hyperfiltration. Whether high protein intake and/or chronic dehydration are associated with hyperfiltration and long-term renal function in children with kidney stones will be an area for future research.

Upper metastable limit osmolality of urine as a predictor of kidney stone formation in children

High fluid intake has been universally recommended for kidney stone prophylaxis. We evaluated 24-h urine osmolality regarded as the best biomarker of optimal hydration and upper metastable limit osmolality after water evaporation from urine sample to the onset of spontaneous crystallization and its usefulness as a new risk index that would describe an individual lithogenic potential. We collected 24-h urine from 257 pediatric patients with kidney stones and 270 controls. After volume and osmolality assessment, the urine samples were subjected to volume reduction in vacuum rotavapor continued to the onset of an induced urinary crystallization. The upper metastable limit osmolality of urine sample was calculated based on its initial osmolality value and the amount of water reduction. Pediatric stone formers presented with higher urine volume and lower urine osmolality than healthy controls. Despite that, their urine samples required much lower volume reduction to induce the spontaneous crystallization than those of controls. The ROC analysis revealed an AUC for the upper metastable limit osmolality of 0.9300 (95% CI 0.9104-0.9496) for distinguishing between stone formers and healthy subjects. At the cutoff of 2696 mOsm/kg, the test provided sensitivity and specificity of 0.8638 and 0.8189, respectively. 24-h urine osmolality provided the information about current hydration status, whereas evaporation test estimated the urinary potential to crystalize dependent on urine composition. Upper metastable limit osmolality may estimate the individual lithogenic capability and identify people at risk to stone formation when exposed to dehydration.

Exposure to organophosphorus pesticides in Norwegian mothers and their children: Diurnal variability in concentrations of their biomarkers and associations with food consumption

Several studies have suggested that exposure to organophosphorus (OP) pesticides is detrimental for health, and in particular for children where moderate doses may have a negative impact on the neurodevelopment. This study surveys levels of the 6 non-specific urinary metabolites (dialkyl phosphates (DAPs)) of OP pesticides in Norwegian mothers (n=48) and their children (n=54), and examines the diurnal variation in concentrations as well as associations with consumption of specific food products. The highest median concentration measured in urine was found for dimethyl thiophosphate (5.3 and 5.5ng/mL_SG; specific gravity corrected) for both children and mothers, respectively, followed by diethyl phosphate (3.8 and 5.3ng/mL_SG, respectively). The intra-class correlation coefficients of DAPs among mothers were moderate (0.49-0.68), and consumption of fruit explained between 8% and 55% of the variations in the mothers' and their children's urinary DAP concentrations.

Phthalates, non-phthalate plasticizers and bisphenols in Swedish preschool dust in relation to children's exposure

Children are exposed to a wide range of chemicals in their everyday environments, including the preschool. In this study, we evaluated the levels of phthalates, non-phthalate plasticizers and bisphenols in dust from 100 Swedish preschools and identified important exposure factors in the indoor environment. In addition, children's total exposure to these chemicals was determined by urine analysis to investigate their relation with dust exposure, and to explore the time trends by comparing with children who provided urine fifteen years earlier. The most abundant plasticizers in preschool dust were the phthalates di-isononyl phthalate (DiNP) and di-(2-ethylhexyl) phthalate (DEHP) with geometric mean levels of 450 and 266μg/g dust, respectively, and the non-phthalate plasticizers bis(2-ethylhexyl) terephthalate (DEHT) and diisononylcyclohexane-1,2-dicarboxylate (DiNCH) found at 105 and 73μg/g dust, respectively. The levels of several substitute plasticizers were higher in newer preschools, whereas the levels of the strictly regulated phthalate di-n-butyl phthalate (DnBP) were higher in older preschools. The presence of foam mattresses and PVC flooring in the sampling room were associated with higher levels of DiNP in dust. Children's exposure from preschool dust ingestion was below established health based reference values and the estimated exposure to different phthalates and BPA via preschool dust ingestion accounted for 2-27% of the total exposure. We found significantly lower urinary levels of BPA and metabolites of strictly regulated phthalates, but higher levels of DiNP metabolites, in urine from the children in this study compared to the children who provided urine samples fifteen years earlier.

Antibiotics in Drinking Water in Shanghai and Their Contribution to Antibiotic Exposure of School Children

A variety of antibiotics have been found in aquatic environments, but antibiotics in drinking water and their contribution to antibiotic exposure in human are not well-explored. For this, representative drinking water samples and 530 urine samples from schoolchildren were selected in Shanghai, and 21 common antibiotics (five macrolides, two β-lactams, three tetracyclines, four fluoquinolones, four sulfonamides, and three phenicols) were measured in water samples and urines by isotope dilution two-dimensional ultraperformance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry. Drinking water included 46 terminal tap water samples from different spots in the distribution system of the city, 45 bottled water samples from 14 common brands, and eight barreled water samples of different brands. Of 21 antibiotics, only florfenicol and thiamphenicol were found in tap water, with the median concentrations of 0.0089 ng/mL and 0.0064 ng/mL, respectively; only florfenicol was found in three bottled water samples from a same brand, with the concentrations ranging from 0.00060 to 0.0010 ng/mL; no antibiotics were found in barreled water. In contrast, besides florfenicol and thiamphenicol, an additional 17 antibiotics were detected in urine samples, and the total daily exposure doses and detection frequencies of florfenicol and thiamphenicol based on urine samples were significantly and substantially higher than their predicted daily exposure doses and detection frequencies from drinking water by Monte Carlo Simulation. These data indicated that drinking water was contaminated by some antibiotics in Shanghai, but played a limited role in antibiotic exposure of children.

Exposure of Preschool-Age Greek Children (RHEA Cohort) to Bisphenol A, Parabens, Phthalates, and Organophosphates

Phthalate esters (PEs), bisphenol A (BPA), and parabens (PBs), which are used in numerous consumer products, are known for their endocrine disrupting properties. Organophosphate chemicals (OPs), which form the basis of the majority of pesticides, are known for their neurotoxic activity in humans. All of these chemicals are associated with health problems to which children are more susceptible. Once they enter the human body, PEs, BPA, PBs, and OPs are metabolized and/or conjugated and finally excreted via urine. Hence, human exposure to these substances is examined through a determination of the urinary concentrations of their metabolites. This study assessed the exposure of Greek preschool-age children to PEs, BPA, PBs, and OPs by investigating the urinary levels of seven PEs metabolites, six PBs, BPA, and six dialkyl phosphate metabolites in five-hundred samples collected from 4-year-old children, subjects of the "RHEA" mother-child cohort in Crete, Greece. Daily intake of endocrine disruptors, calculated for 4 year old children, was lower than the corresponding daily intake for 2.5 year old children, which were determined in an earlier study of the same cohort. In some cases the daily intake levels exceeded the U.S. Environmental Protection Agency Tolerable Daily Intake (TDI) values and the EFSA Reference Doses (RfD) (e.g., for di-2-ethyl-hexyl phthalate, 3.6% and 1% of the children exceeded RfD and TDi, respectively). Exposure was linked to three main sources: PEs-BPA to plastic, PBs-diethyl phthalate to personal hygiene products, and OPs to food.

Phthalate esters, parabens and bisphenol-A exposure among mothers and their children in Greece (Rhea cohort)

Exposure to endocrine disruptors, used as additives, preservatives, plasticisers and solvents in numerous consumer products, might cause adverse health effects. Humans exposed to these chemicals, metabolise and excrete them mostly via urine. Urinary metabolite concentrations are used as biomarkers of exposure. We evaluated the exposure of 4-month pregnant women and their children at 2 years of age to phthalates, parabens and bisphenol-A. Concentrations of eight phthalate metabolites, six parabens and bisphenol-A were measured in 239 mother-child pairs of the "Rhea" cohort in Greece. Concentration levels in mother and children were comparable with corresponding concentrations in other countries worldwide. Low Spearman correlation coefficients (CC 0.1-0.2, p-value < 0.01) were observed for di-ethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl-benzyl phthalate (BBP) and ethyl paraben (EPB) between mothers and their children. We observed higher median daily intake (DIu) for mothers (e.g. di-ethyl phthalate 6.9 μg d(-1) kg(-1)) than for their children (1.4 μg d(-1) kg(-1)) for all examined compounds, except for di-2-ethylhexyl phthalate (DEHP) and bisphenol-A. Principal component analysis (PCA) indicated two main sources of exposure (plastic related and personal care-hygiene products) for phthalates, parabens and bisphenol-A. Differences in DEHP metabolism were observed among mothers-children and female-male children.

Human exposure pathways to organophosphate triesters - a biomonitoring study of mother-child pairs

The worldwide ban of several formulations of brominated flame retardants has caused an increase in the production of organophosphorus flame retardants (PFRs) to meet the existing fire regulations for a wide range of household products. This biomonitoring study surveys the occurrence of the metabolites from PFRs and related plasticizers (dialkyl and diaryl phosphates; DAPs) in urine from a Norwegian mother-child cohort (48 mothers and 54 children). Concentrations of DAPs were higher in the children than in their mothers (Wilcoxon signed-rank test p=0.001). Median urinary concentrations of diphenyl phosphate (DPHP) were 1.1 and 0.51ng/mL in children and mothers, respectively, followed by bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) with medians of 0.23 and 0.12ng/mL, respectively. Detection frequencies for bis(2-butoxyethyl) phosphate (BBOEP) in urine from children and mothers were 32 and 1%, respectively (median<0.18ng/mL), and for di-n-butyl phosphate (DNBP) 15 and 8%, respectively (median<0.12ng/mL). The concentrations of DPHP and BDCIPP in urine from children were significantly correlated with those found for their parent compounds in air and dust from the households (Spearman's rank correlations 0.30<Rs<0.36; p<0.05). For mothers, only the urinary concentration of BDCIPP was correlated to its precursor in dust from the households (Rs=0.40; p<0.01), which might indicate higher impact of the household environment on children than mothers. A diurnal variability study of the mothers' urinary concentrations of DPHP and BDCIPP showed lower concentrations at time periods when women were likely to be outside the household. In contrast, no relevant associations between organophosphate metabolites in urine and food consumption data obtained through a 24hour recall were seen. This suggests that the residential environment is a more important exposure pathway to PFRs than the diet.

Using urinary biomarkers to evaluate polycyclic aromatic hydrocarbon exposure in 126 preschool children in Ohio

Limited data exist on exposures of young children to polycyclic aromatic hydrocarbons (PAHs) in the United States (US). The urinary metabolite of pyrene, 1-hydroxypyrene (1-OHPyr), is widely used as a biomarker of total PAH exposure. Our objectives were to quantify urinary 1-OHPyr levels in 126 preschool children over a 48-h period and to examine associations between selected sociodemographic/lifestyle factors and urinary 1-OHPyr levels. Monitoring was performed at 126 homes and 16 daycares in Ohio in 2001, and questionnaires and urine samples were collected. The median urinary 1-OHPyr level was 0.33 ng/mL. In a multiple regression model, sampling season (p = 0.0001) and natural log (ln)-transformed creatinine concentration (p = 0.0006) were highly significant predictors of ln-transformed 1-OH-Pyr concentration; cooking appliance type (p = 0.096) was a marginally significant predictor of ln(1-OHPyr). These children had higher median urinary 1-OHPyr levels compared to other US children (≤ 0.15 ng/mL) in previously published studies, which suggests possible geographical differences in PAH exposure.

Short-term variability and predictors of urinary pentachlorophenol levels in Ohio preschool children

Pentachlorophenol (PCP) is a persistent and ubiquitous environmental contaminant. No published data exist on the temporal variability or important predictors of urinary PCP concentrations in young children. In this further analysis of study data, we have examined the associations between selected sociodemographic or lifestyle factors and urinary PCP concentrations in 115 preschool children over a 48-h period and assessed the 48-hour variability of urinary PCP levels in a subset of 15 children. Monitoring was performed at 115 homes and 16 daycares in Ohio (USA) in 2001. Questionnaires/diaries and spot urine samples were collected from each child. The median urinary PCP level was 0.8 ng/mL (range < 0.2-23.8 ng/mL). The intraclass correlation coefficient for urinary PCP was 0.42, which indicates fairly low reliability for a single sample over a 48-h period. In a multiple regression model, age of home and ln(creatinine levels) were significant predictors and sampling season, time spent outside, and pet ownership were marginally significant predictors of ln(urinary PCP levels), collectively explaining 29% of the variability of PCP in urine. To adequately assess short-term exposures of children to PCP, several spot urine measurements are likely needed as well as information regarding residence age, seasonality, time spent outdoors, and pet ownership.

Organophosphate flame retardants and plasticizers in the air and dust in German daycare centers and human biomonitoring in visiting children (LUPE 3)

Organophosphate (OP) flame retardants and plasticizers are chemicals that have been used in large quantities in diverse consumer and building-related products for decades. In the present study, OPs were measured in paired indoor air and dust samples from 63 daycare centers in Germany. Moreover, the urine of 312 children between 22 and 80 months old who attend these facilities was analyzed for the presence of eight OP metabolites. Tri-(2-butoxyethyl)-phosphate (TBEP), tris-(2-chloroisopropyl) phosphate (TCPP), and tri-n-butyl-phosphate (TnBP) were present in low concentrations in indoor air, with median values of 49 ng/m(3), 2.7 ng/m(3), and 2.2 ng/m(3), respectively. In dust, median values of 225 mg/kg for TBEP, 2.7 mg/kg for TCPP, 1.1mg/kg for diphenyl(2-ethylhexyl) phosphate, and 0.5mg/kg for tri-phenyl-phosphate (TPhP) were found. In the urine samples, the metabolites di-phenyl-phosphate, di-n-butyl-phosphate, and di-(2-butoxyethyl)-phosphate had median values (95th percentiles) of 0.8 μg/l (4.0 μg/l), 0.2 μg/l (0.9 μg/l), and 2.0 μg/l (10.7 μg/l), respectively. A significant correlation was found between the dust and air samples in the levels of TnBP, tris(2-chloroethyl) phosphate (TCEP), and TBEP. For TCEP and TBEP, significant correlations were also observed between the levels in dust and the respective metabolite levels in urine. For TCEP, there was also a significant correlation between the concentration in indoor air and metabolite levels in urine. Based on the 95th percentile in dust and air in our study and data from residences in a previously published study, the daily intake of the most abundant OP (TBEP) is high (i.e., 3.2 μg/kg b.w.). This level is approximately 6.4% of the reference dose (RfD) established by the NSF, U.S.A. Overall, our study shows that daycare centers are indoor environments that contribute to OP exposure.

Evaluation and medical management of kidney stones in children

PURPOSE

We review the current literature on the diagnostic evaluation and dietary and pharmacological management of children with nephrolithiasis.

MATERIALS AND METHODS

We searched MEDLINE(®), Embase(®) and the Cochrane Library from their inceptions to March 2014 for published articles in English on kidney stones and therapy in children 0 to 18 years old. Based on review of the titles and abstracts, 110 of the 1,014 articles (11%) were potentially relevant to the diagnostic evaluation and medical management of nephrolithiasis in children. We summarized this literature and drew on studies performed in adult populations to augment areas in which no studies of sufficient quality have been performed in children, and to highlight areas in need of research.

RESULTS

During the last 25 years the incidence of nephrolithiasis in children has increased by approximately 6% to 10% annually and is now 50 per 100,000 adolescents. Kidney stones that form during childhood have a similar composition to those that form in adulthood. Approximately 75% to 80% of stones are composed of predominantly calcium oxalate, 5% to 10% are predominantly calcium phosphate, 10% to 20% are struvite and 5% are pure uric acid. The recurrence rate of nephrolithiasis in patients with stones that form during childhood is poorly defined. Ultrasound should be used as the initial imaging study to evaluate children with suspected nephrolithiasis, with noncontrast computerized tomography reserved for those in whom ultrasound is nondiagnostic and the suspicion of nephrolithiasis remains high. Current treatment strategies for children with kidney stone disease are based largely on extrapolation of studies performed in adult stone formers and single institution cohort or case series studies of children. Tamsulosin likely increases the spontaneous passage of ureteral stones in children. Increased water intake and reduction of salt consumption should be recommended for all children with a history of kidney stones. Potassium citrate is a potentially effective medication for children with calcium oxalate stones and concomitant hypocitraturia, as well as children with uric acid stones. However, long-term compliance with therapy and the effect on decreasing stone recurrence in children are unknown. Based largely on efficacy in adult populations, thiazide diuretics should be considered in the treatment of children with calcium based stones and persistent hypercalciuria refractory to reductions in salt intake.

CONCLUSIONS

The incidence of kidney stone disease in children is increasing, yet few randomized clinical trials or high quality observational studies have assessed whether dietary or pharmacological interventions decrease the recurrence of kidney stones in children. Collaborative efforts and randomized clinical trials are needed to determine the efficacy and effectiveness of alternative treatments for children with nephrolithiasis, particularly those with calcium oxalate stones and concomitant hypercalciuria and hypocitraturia. Additional areas in need of study are the optimal length of time for a trial of stone passage in children, the cost-effectiveness of medical expulsive therapy vs analgesics alone, and the size and location of stones for which medical expulsive therapy is most effective.

Current medical treatment in pediatric urolithiasis

Although the prevalence of urolithiasis is nearly 2-3% in childhood, the risk of recurrence may range from 6.5-54%. There has been an increase in urinary stone disease among pediatric age groups, and stone disease has a multifactorial etiology. After the diagnosis, detailed metabolic evaluation is required. High recurrence rates, therapeutic irregularities and deficiency in diagnosis may lead to comorbidities such as loss of kidney function. Following diagnosis, the requirement for surgery, such as stone extraction and correction of anatomical anomalies, is determined. Medical and supportive treatments are also needed to prevent recurrence and urinary tract infections and to preserve renal function. Supportive care includes increased fluid intake and dietary modifications. Medical treatment is dependent on the cause of the urinary stone disease. The morbidities associated with pediatric urolithiasis can be prevented by early diagnosis, detailed metabolic analysis, regular follow-up and medical treatment protocols.

Phthalates in German daycare centers: occurrence in air and dust and the excretion of their metabolites by children (LUPE 3)

Phthalates have been used for decades in large quantities, leading to the ubiquitous exposure of the population. In an investigation of 63 German daycare centers, indoor air and dust samples were analyzed for the presence of 10 phthalate diesters. Moreover, 10 primary and secondary phthalate metabolites were quantified in urine samples from 663 children attending these facilities. In addition, the urine specimens of 150 children were collected after the weekend and before they went to daycare centers. Di-isobutyl phthalate (DiBP), dibutyl phthalate (DnBP), and di-2-ethylhexyl phthalate (DEHP) were found in the indoor air, with median values of 468, 227, and 194ng/m(3), respectively. In the dust, median values of 888mg/kg for DEHP and 302mg/kg for di-isononyl phthalate (DiNP) were observed. DnBP and DiBP were together responsible for 55% of the total phthalate concentration in the indoor air, whereas DEHP and DiNP were responsible for 70% and 24% of the total phthalate concentration in the dust. Median concentrations in the urine specimens were 44.7μg/l for the DiBP monoester, 32.4μg/l for the DnBP monoester, and 16.5μg/l and 17.9μg/l for the two secondary DEHP metabolites. For some phthalates, we observed significant correlations between their concentrations in the indoor air and dust and their corresponding metabolites in the urine specimens using bivariate analyses. In multivariate analyses, the concentrations in dust were not associated with urinary metabolite excretion after controlling for the concentrations in the indoor air. The total daily "high" intake levels based on the 95th percentiles calculated from the biomonitoring data were 14.1μg/kg b.w. for DiNP and 11.9μg/kg b.w. for DEHP. Compared with tolerable daily intake (TDI) values, our "high" intake was 62% of the TDI value for DiBP, 49% for DnBP, 24% for DEHP, and 9% for DiNP. For DiBP, the total daily intake exceeded the TDI value for 2.4% of the individuals. Using a cumulative risk-assessment approach for the sum of DEHP, DnBP, and DiBP, 20% of the children had concentrations exceeding the hazard index of one. Therefore, a further reduction of the phthalate exposure of children is needed.

Children's phthalate intakes and resultant cumulative exposures estimated from urine compared with estimates from dust ingestion, inhalation and dermal absorption in their homes and daycare centers

Total daily intakes of diethyl phthalate (DEP), di(n-butyl) phthalate (DnBP), di(isobutyl) phthalate (DiBP), butyl benzyl phthalate (BBzP) and di(2-ethylhexyl) phthalate (DEHP) were calculated from phthalate metabolite levels measured in the urine of 431 Danish children between 3 and 6 years of age. For each child the intake attributable to exposures in the indoor environment via dust ingestion, inhalation and dermal absorption were estimated from the phthalate levels in the dust collected from the child's home and daycare center. Based on the urine samples, DEHP had the highest total daily intake (median: 4.42 µg/d/kg-bw) and BBzP the lowest (median: 0.49 µg/d/kg-bw). For DEP, DnBP and DiBP, exposures to air and dust in the indoor environment accounted for approximately 100%, 15% and 50% of the total intake, respectively, with dermal absorption from the gas-phase being the major exposure pathway. More than 90% of the total intake of BBzP and DEHP came from sources other than indoor air and dust. Daily intake of DnBP and DiBP from all exposure pathways, based on levels of metabolites in urine samples, exceeded the Tolerable Daily Intake (TDI) for 22 and 23 children, respectively. Indoor exposures resulted in an average daily DiBP intake that exceeded the TDI for 14 children. Using the concept of relative cumulative Tolerable Daily Intake (TDI(cum)), which is applicable for phthalates that have established TDIs based on the same health endpoint, we examined the cumulative total exposure to DnBP, DiBP and DEHP from all pathways; it exceeded the tolerable levels for 30% of the children. From the three indoor pathways alone, several children had a cumulative intake that exceeded TDI(cum). Exposures to phthalates present in the air and dust indoors meaningfully contribute to a child's total intake of certain phthalates. Such exposures, by themselves, may lead to intakes exceeding current limit values.

Risk factors for urinary stones in healthy schoolchildren with and without a family history of nephrolithiasis

BACKGROUND

The prevalence of lithiasis is increasing at all ages. This study aimed to assess the crystallization risk in urine from healthy school children and to determine urinary parameters that are most associated with it.

METHODS

Urine samples were obtained from 184 children aged 5-12 years: a spot sample collected in the afternoon, and a 12-h overnight sample. Information was obtained regarding family histories of lithiasis. Urine volume, pH, and biochemical parameters of stone risk were measured. Crystallization risk was defined by the presence of specific urine conditions that had previously been associated with stone formation in vitro.

RESULTS

Crystallization risk was observed in 15 % of spot urine samples and 54 % of 12-h samples. Metabolic abnormalities and a low urinary volume were more frequently detected in children with crystallization risk. Calcium excretion and calcium/citrate ratio were higher in children with a family history of lithiasis.

CONCLUSIONS

We observed a high prevalence of crystallization risk in urine, especially in children with a family history of the disease. Low urinary volume was the factor most associated with increased risk. Adequate fluid intake at an early age may be a simple and effective measure to reduce the incidence of nephrolithiasis.

Pediatric primary urolithiasis: 12-year experience at a Midwestern Children's Hospital

PURPOSE

Due to environmental and social changes (and possibly obesity) as new risk factors for stone formation in adults and changes in imaging techniques, we assessed whether etiologies of primary pediatric urolithiasis have changed, and if relationships exist between the condition and obesity or imaging technique.

MATERIALS AND METHODS

All pediatric patients with documented primary urolithiasis who underwent serum and 24-hour urine analyses between 1999 and 2010 were evaluated. Age at diagnosis, gender, body mass index and imaging technique were recorded.

RESULTS

Of the 222 patients (48% male) all had normal serum creatinine, electrolytes and minerals. Primary pediatric urolithiasis was diagnosed by ultrasound in 73% of cases and computerized tomography in 27%. Mean ± SD annual incidence of urolithiasis per 1,000 clinic visits increased from 2.4 ± 1.5 in the first half of the study period to 6.2 ± 2.1 in the second half (p <0.005). Mean ± SD age at diagnosis was 11.8 ± 3.8 years and body mass index was 21.7 ± 5.7 (rate of overweight 15%). A total of 140 patients had urine output less than 1.0 ml/kg per hour, with this being the only abnormality in 54. Hypercalciuria was observed in 46% of patients, hypocitraturia in 10% and high calcium-to-citrate ratio in 51%. Mild absorptive hyperoxaluria was noted in 3 patients and hyperuricosuria in 11, with all 14 exhibiting at least 1 additional abnormality. Cystinuria was present in 1 patient. No etiology was identified in 20 patients (9.0%).

CONCLUSIONS

Oliguria and hypercalciuria continue to be the most common etiologies of pediatric primary urolithiasis, followed by hypocitraturia. The recent increase in stone incidence is unlikely due to increased use of computerized tomography. Incidence of obesity was not higher than in the general population. Hyperoxaluria and cystinuria are rare, and thus might not be indicated in the initial analysis.

Pediatric urolithiasis: causative factors, diagnosis and medical management

Childhood urolithiasis is associated with considerable morbidity and recurrence. Many risk factors--including those metabolic, genetic, anatomic, dietary and environmental in nature--have been identified in children with urinary tract calculi. As pediatric urolithiasis with a metabolic etiology is the most common disease, evaluating the metabolic risk factors in patients is necessary to both effectively treat current stones and prevent recurrence. We discuss causative risk factors of pediatric urolithiasis, as well as the diagnostic and therapeutic approaches.

An update on the changing epidemiology and metabolic risk factors in pediatric kidney stone disease

Nephrolithiasis in children is a painful and costly disease that may also have detrimental long-term effects on kidney function. Recent data provide evidence that the incidence of nephrolithiasis in children is rising. Children who are white, female, and adolescent seem to have the highest risk for forming symptomatic kidney stones. Although the reasons for the rising incidence and demographic discrepancies in pediatric nephrolithiasis are not yet clear, recent investigations into urine chemistry provide clues regarding predisposing metabolic risk factors. As more data emerge regarding epidemiologic and metabolic characteristics of pediatric kidney stone formers, we hope to gain a better understanding of the causes of kidney stone disease and, ultimately, provide better strategies for stone prevention in children.

Assessing the quantitative relationships between preschool children's exposures to bisphenol A by route and urinary biomonitoring

Limited published information exists on young children's exposures to bisphenol A (BPA) in the United States using urinary biomonitoring. In a previous project, we quantified the aggregate exposures of 257 preschool children to BPA in environmental and personal media over 48-h periods in 2000-2001 at homes and daycares in North Carolina and Ohio. In the present study for 81 Ohio preschool children ages 23-64 months, we quantified the children's urinary total BPA (free and conjugated) concentrations over these same 48-h periods in 2001. Then, we examined the quantitative relationships between the children's intakes doses of BPA through the dietary ingestion, nondietary ingestion, and inhalation routes and their excreted amounts of urinary BPA. BPA was detected in 100% of the urine samples. The estimated median intake doses of BPA for these 81 children were 109 ng/kg/day (dietary ingestion), 0.06 ng/kg/day (nondietary ingestion), and 0.27 ng/kg/day (inhalation); their estimated median excreted amount of urinary BPA was 114 ng/kg/day. Our multivariable regression model showed that dietary intake of BPA (p = 0.04) and creatinine concentration (p = 0.004) were significant predictors of urinary BPA excretion, collectively explaining 17% of the variability in excretion. Dietary ingestion of BPA accounted for >95% of the children's excreted amounts of urinary BPA.

The reliability of using urinary biomarkers to estimate children's exposures to chlorpyrifos and diazinon

A few studies have reported concurrent levels of chlorpyrifos (CPF) and diazinon (DZN) and their environmentally occurring metabolites, 3,5,6-trichloro-2-pyridinol (TCP) and 2-isopropyl-6-methyl-4-pyrimidinol (IMP), in food and in environmental media. This information raises questions regarding the reliability of using these same metabolites, TCP and IMP, as urinary biomarkers to quantitatively assess the everyday exposures of children to CPF and DZN, respectively. In this study, we quantified the distributions of CPF, DZN, TCP, and IMP in several environmental and personal media at the homes and day-care centers of 127 Ohio preschool children and identified the important sources and routes of their exposures. The children were exposed to concurrent levels of these four chemicals from several sources and routes at these locations. DZN and IMP were both detected above 50% in the air and dust samples. CPF and TCP were both detected in greater than 50% of the air, dust (solid), food, and hand wipe samples. TCP was detected in 100% of the urine samples. Results from our regression models showed that creatinine levels (<0.001), and dietary (P<0.001) and inhalation (P<0.10) doses of TCP were each significant predictors of urinary TCP, collectively explaining 27% of the urinary TCP variability. This information suggests that measurement of urinary TCP did not reliably allow quantitative estimation of the children's everyday environmental exposures to CPF.

Exposures of preschool children to chlorpyrifos, diazinon, pentachlorophenol, and 2,4-dichlorophenoxyacetic acid over 3 years from 2003 to 2005: A longitudinal model

The impact of the US EPA-required phase-outs starting in 2000-2001 of residential uses of the organophosphate (OP) pesticides chlorpyrifos (CPF) and diazinon (DZN) on preschool children's pesticide exposures was investigated over 2003-2005, in the Raleigh-Durham-Chapel Hill area of North Carolina. Data were collected from 50 homes, each with a child initially of age 3 years (OCh) and a younger child (YCh). Environmental samples (indoor and outdoor air, dust, soil) and child-specific samples (hand surface residue, urine, diet) were collected annually over 24-h periods at each home. Child time-activity diaries and household pesticide use information were also collected. Analytes included CPF and DZN; pentachlorophenol (PCP); 2,4-dichlorophenoxyacetic acid (2,4-D); the CPF metabolite 3,5,6-trichloro-2-pyridinol (TCP); and the DZN metabolite 2-isopropyl-6-methyl-4-pyrimidinol (IMP). Exposures (ng/day) through the inhalation, dietary ingestion, and indirect ingestion were calculated. Aggregate potential doses in ng/kg body weight per day (ng/kg/day) were obtained by summing the potential doses through the three routes of exposure. Geometric mean aggregate potential doses decreased from 2003 to 2005 for both OCh and YCh, with the exception of 2,4-D. Child-specific longitudinal modeling indicated significant declines across time of the potential doses of CPF, DZN, and PCP for both children; declines of IMP for both children, significant only for OCh; a decline of TCP for OCh but an increase of TCP for YCh; and no significant change of 2,4-D for either child. Age-adjusted modeling indicated significant effects of the child's age for all except CPF, and of time for all except PCP and 2,4-D. Within-home variability was small compared with that between homes; variability was smallest for 2,4-D, both within and between homes. The aggregate potential doses of CPF and DZN were well below published reference dose values. These findings show the success of the US EPA restrictions in reducing young children's pesticide exposures.

Medical treatment of pediatric urolithiasis

In recent years the incidence of pediatric stone disease has increased several fold, mostly due to hypercalciuria and hypocitraturia. The goal of medical treatment is to protect the patient from formation of new stones and expansion of existing ones. The non-pharmacological means to address stone disease include high fluid intake and, frequently, modification of nutritional habits. The pharmacological treatment is based on the chemical composition of the stone and the biochemical abnormalities causing its formation; hence, chemical analysis of the stone, urine and blood is of paramount importance and should be done when the first stone is detected. This review discusses the current options of medical treatment of pediatric urolithiasis.

Adult and children's exposure to 2,4-D from multiple sources and pathways

In this study, we investigated the 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide exposures of 135 preschool-aged children and their adult caregivers at 135 homes in North Carolina (NC) and Ohio (OH). Participants were randomly recruited from six NC and six OH counties. Monitoring was performed over a 48-h period at the participants' homes. Environmental samples included soil, outdoor air, indoor air, and carpet dust. Personal samples collected by the adult caregivers concerning themselves and their children consisted of solid food, liquid food, hand wipe, and spot urine samples. All samples were analyzed for 2,4-D (free acid form) by gas chromatography/mass spectrometry. 2,4-D was detected in all types of environmental samples but most often in carpet dust samples, with detection frequencies of 83% and 98% in NC and OH, respectively. The median level of 2,4-D in the carpet dust samples was about three times higher in OH homes compared to NC homes (156 vs. 47.5 ng/g, P<0.0002). For personal samples, 2,4-D was more frequently detected in the hand wipe samples from OH participants (>48%) than from NC participants (<9%). Hand wipe levels at the 95th percentile were about five times higher for OH children (0.1 ng/cm(2)) and adults (0.03 ng/cm(2)) than for the NC children (0.02 ng/cm(2)) and adults (<0.005 ng/cm(2)). 2,4-D was detected in more than 85% of the child and adult urine samples in both states. The median urinary 2,4-D concentration was more than twice as high for OH children compared to NC children (1.2 vs. 0.5 ng/ml, P<0.0001); however, the median concentration was identical at 0.7 ng/ml for both NC and OH adults. The intraclass correlation coefficient of reliability for an individual's urinary 2,4-D measurements, estimated from the unadjusted (0.31-0.62) and specific gravity-adjusted (0.37-0.73) values, were somewhat low for each group in this study. The variability in urinary 2,4-D measurements over the 48-h period for both children and adults in NC and OH suggests that several spot samples were needed to adequately assess these participants' exposures to 2,4-D in residential settings. Results from this study showed that children and their adult caregivers in NC and OH were likely exposed to 2,4-D through several pathways at their homes. In addition, our findings suggest that the OH children might have been exposed to higher levels of 2,4-D through the dermal and nondietary routes of exposure than the NC children and the NC and OH adults.

An observational study of 127 preschool children at their homes and daycare centers in Ohio: environmental pathways to cis- and trans-permethrin exposure

The potential exposures of 127 preschool children to the pyrethroid insecticides, cis- and trans-permethrin, in their everyday environments were examined. Participants were recruited randomly from 127 homes and 16 daycare centers in six Ohio (OH) counties. Monitoring was performed over a 48-h period at the children's homes and/or daycare centers. Samples collected included soil, carpet dust, indoor air, outdoor air, diet, hand wipes, surface wipes, transferable residues, and urine. The environmental samples were analyzed for the cis and trans isomers of permethrin, and the urine samples were analyzed for the pyrethroid urinary metabolite, 3-phenoxybenzoic acid (3-PBA), by gas chromatography/mass spectrometry. The isomers were detected most often in the dust (100%) and hand wipe (>78%) samples collected at both homes and daycare centers. The median levels of cis-permethrin (470 and 1010 ng/g) were higher than the median levels of trans-permethrin (344 and 544 ng/g) in the dust samples at both the children's homes and daycare centers, respectively. In the children's hand wipe samples, the median levels of cis- and trans-permethrin were similar, ranging from 0.03 to 0.04 ng/cm(2), at both locations. The urinary metabolite 3-PBA was detected in 67% of the children's urine samples. The median urinary 3-PBA concentration for the children was 0.3 ng/mL, and the maximum value for one child was 33.8 ng/mL. The primary route of the children's exposure to the combined isomers was through dietary ingestion, followed by indirect ingestion. In addition, our calculated aggregate absorbed doses of permethrin accounted for about 60% of the excreted amounts of 3-PBA found in the children's urine. In conclusion, these children were potentially exposed to low levels of permethrin from several sources, and through several pathways and routes.

An observational study of the potential exposures of preschool children to pentachlorophenol, bisphenol-A, and nonylphenol at home and daycare

The Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study investigated the potential exposures of 257 preschool children, ages 1 1/2-5 yr, and their primary adult caregivers to more than 50 anthropogenic chemicals. Field sampling took place in selected counties in North Carolina (NC) and Ohio (OH) in 2000-2001. Over a 48-h period in each child's daycare center and/or home, food, beverages, indoor air, outdoor air, house dust, soil, participants' hand surfaces and urine were sampled. Additional samples-transferable residues, food preparation surface wipes, and hard floor surface wipes-were collected in the approximately 13% of the homes that had pesticide applications within the 7 days prior to field sampling. Three phenols were among the measured chemicals: pentachlorophenol (PCP), bisphenol-A [2,2-bis(4-hydroxyphenyl)propane], and nonylphenol (4-n-nonylphenol). Nonylphenol (NP) was detected in less than 11% of the samples in any medium. Among samples that were collected at all participants' homes and daycare centers, PCP was detected in >50% of indoor air, outdoor air, house dust, and urine samples; bisphenol-A (BPA) was detected in >50% of indoor air, hand wipe, solid food, and liquid food samples. The concentrations of the phenols in the sampled media were measured, and the children's potential exposures and potential absorbed doses resulting from intake through the inhalation, dietary ingestion, and indirect ingestion routes of exposure were estimated. The children's potential exposures to PCP were predominantly through inhalation: 78% in NC and 90% in OH. In contrast, their potential exposures to BPA were predominantly through dietary ingestion: 99%, for children in both states. The children's estimated exposures to PCP, calculated from the amounts excreted in their urine, exceeded their estimated maximum potential intake, calculated from the multimedia PCP concentrations, by a factor greater than 10. This inconsistency for PCP highlights the need for further research on the environmental pathways and routes of PCP exposure, investigation of possible exposures to other compounds that could be metabolized to PCP, and on the human absorption, metabolism, and excretion of this phenol over time periods longer than 48 h.

Physiology of epithelial Ca2+ and Mg2+ transport

Ca2+ and Mg2+ are essential ions in a wide variety of cellular processes and form a major constituent of bone. It is, therefore, essential that the balance of these ions is strictly maintained. In the last decade, major breakthrough discoveries have vastly expanded our knowledge of the mechanisms underlying epithelial Ca2+ and Mg2+ transport. The genetic defects underlying various disorders with altered Ca2+ and/or Mg2+ handling have been determined. Recently, this yielded the molecular identification of TRPM6 as the gatekeeper of epithelial Mg2+ transport. Furthermore, expression cloning strategies have elucidated two novel members of the transient receptor potential family, TRPV5 and TRPV6, as pivotal ion channels determining transcellular Ca2+ transport. These two channels are regulated by a variety of factors, some historically strongly linked to Ca2+ homeostasis, others identified in a more serendipitous manner. Herein we review the processes of epithelial Ca2+ and Mg2+ transport, the molecular mechanisms involved, and the various forms of regulation.

The epithelial calcium channels TRPV5 and TRPV6: regulation and implications for disease

The epithelial Ca(2+) channels TRPV5 and TRPV6 represent a new family of Ca(2+) channels that belongs to the superfamily of transient receptor potential channels. TRPV5 and TRPV6 constitute the apical Ca(2+) entry mechanism in active Ca(2+) transport in kidney and intestine. The central role of TRPV5 and TRPV6 in active Ca(2+) (re)absorption makes it a prime target for regulation to maintain Ca(2+) balance. This review covers the hormonal regulation, interaction with accessory proteins and (patho)physiological implications of these epithelial Ca(2+) channels.

Exposures of preschool children to chlorpyrifos and its degradation product 3,5,6-trichloro-2-pyridinol in their everyday environments

As part of the Children's Total Exposure to Persistent Pesticides and Other Persistent Organic Pollutants (CTEPP) study, we investigated the exposures of preschool children to chlorpyrifos and its degradation product 3,5,6-trichloro-2-pyridinol (TCP) in their everyday environments. During this study, the participants were still able to purchase and apply chlorpyrifos at their homes or day care centers. Participants were recruited randomly from 129 homes and 13 day care centers in six North Carolina counties. Monitoring was performed over a 48-h period at the children's homes and/or day care centers. Samples that were collected included duplicate plate, indoor and outdoor air, urine, indoor floor dust, play area soil, transferable residues (PUF roller), and surface wipes (hand, food preparation, and hard floor). The samples were extracted and analyzed by gas chromatography/mass spectrometry. Chlorpyrifos was detected in 100% of the indoor air and indoor floor dust samples from homes and day care centers. TCP was detected at homes and day care centers in 100% of the indoor floor dust and hard floor surface wipe, in >97% of the solid food, and in >95% of the indoor air samples. Generally, median levels of chlorpyrifos were higher than those of TCP in all media, except for solid food samples. For these samples, the median TCP concentrations were 12 and 29 times higher than the chlorpyrifos concentrations at homes and day care centers, respectively. The median urinary TCP concentration for the preschool children was 5.3 ng/ml and the maximum value was 104 ng/ml. The median potential aggregate absorbed dose (ng/kg/day) of chlorpyrifos for these preschool children was estimated to be 3 ng/kg/day. The primary route of exposure to chlorpyrifos was through dietary intake, followed by inhalation. The median potential aggregate absorbed dose of TCP for these children was estimated to be 38 ng/kg/day, and dietary intake was the primary route of exposure. The median excreted amount of urinary TCP for these children was estimated to be 117 ng/kg/day. A full regression model of the relationships among chlorpyrifos and TCP for the children in the home group explained 23% of the variability of the urinary TCP concentrations by the three routes of exposure (inhalation, ingestion, dermal absorption) to chlorpyrifos and TCP. However, a final reduced model via step-wise regression retained only chlorpyrifos through the inhalation route and explained 22% of the variability of TCP in the children's urine. The estimated potential aggregate absorbed doses of chlorpyrifos through the inhalation route were low (median value, 0.8 ng/kg/day) and could not explain most of the excreted amounts of urinary TCP. This suggested that there were other possible sources and pathways of exposure that contributed to the estimated potential aggregate absorbed doses of these children to chlorpyrifos and TCP. One possible pathway of exposure that was not accounted for fully is through the children's potential contacts with contaminated surfaces at homes and day care centers. In addition, other pesticides such as chlorpyrifos-methyl may have also contributed to the levels of TCP in the urine. Future studies should include additional surface measurements in their estimation of potential absorbed doses of preschool children to environmental pollutants. In conclusion, the results showed that the preschool children were exposed to chlorpyrifos and TCP from several sources, through several pathways and routes. .

Enhanced passive Ca2+ reabsorption and reduced Mg2+ channel abundance explains thiazide-induced hypocalciuria and hypomagnesemia

Thiazide diuretics enhance renal Na+ excretion by blocking the Na+-Cl- cotransporter (NCC), and mutations in NCC result in Gitelman syndrome. The mechanisms underlying the accompanying hypocalciuria and hypomagnesemia remain debated. Here, we show that enhanced passive Ca2+ transport in the proximal tubule rather than active Ca2+ transport in distal convolution explains thiazide-induced hypocalciuria. First, micropuncture experiments in mice demonstrated increased reabsorption of Na+ and Ca2+ in the proximal tubule during chronic hydrochlorothiazide (HCTZ) treatment, whereas Ca2+ reabsorption in distal convolution appeared unaffected. Second, HCTZ administration still induced hypocalciuria in transient receptor potential channel subfamily V, member 5-knockout (Trpv5-knockout) mice, in which active distal Ca2+ reabsorption is abolished due to inactivation of the epithelial Ca2+ channel Trpv5. Third, HCTZ upregulated the Na+/H+ exchanger, responsible for the majority of Na+ and, consequently, Ca2+ reabsorption in the proximal tubule, while the expression of proteins involved in active Ca2+ transport was unaltered. Fourth, experiments addressing the time-dependent effect of a single dose of HCTZ showed that the development of hypocalciuria parallels a compensatory increase in Na+ reabsorption secondary to an initial natriuresis. Hypomagnesemia developed during chronic HCTZ administration and in NCC-knockout mice, an animal model of Gitelman syndrome, accompanied by downregulation of the epithelial Mg2+ channel transient receptor potential channel subfamily M, member 6 (Trpm6). Thus, Trpm6 downregulation may represent a general mechanism involved in the pathogenesis of hypomagnesemia accompanying NCC inhibition or inactivation.

Role of urinary supersaturation in the evaluation of children with urolithiasis

Timed urine collections are a standard part of the evaluation for predisposition to stone formation in children with urolithiasis. Supersaturation is defined as the ratio of the concentration of dissolved salt to its solubility in urine. The purpose of the present study was to determine if adding supersaturation to the standard timed urine collection increased the ability to detect a metabolic predisposition to stone formation. Thirty-two children with urolithiasis had 24-hour urine measurements of calcium, oxalate, citrate, uric acid, and cystine (the "traditional" evaluation), as well as supersaturation for calcium oxalate, calcium phosphate, and uric acid, on the same urine sample. Nine (28%) of the 32 were hypercalciuric, 2 (6%) hyperoxaluric, and 4 (12%) hypocitraturic. In total, 14 (44%) had a metabolic predisposition that was detected by the traditional evaluation. Supersaturation was elevated in 18 (56%), including nine who did not have metabolic predisposition detected by traditional evaluation. Urine volume was low in 17 (53%) of 32 children, including eight of nine children with abnormal supersaturation but normal traditional evaluation. Only one child with normal traditional evaluation and normal urine volume had elevated supersaturation. These results show that the benefit of adding supersaturation to the traditional evaluation was largely negated by consideration of urine volume.

Calcium absorption across epithelia

Ca(2+) is an essential ion in all organisms, where it plays a crucial role in processes ranging from the formation and maintenance of the skeleton to the temporal and spatial regulation of neuronal function. The Ca(2+) balance is maintained by the concerted action of three organ systems, including the gastrointestinal tract, bone, and kidney. An adult ingests on average 1 g Ca(2+) daily from which 0.35 g is absorbed in the small intestine by a mechanism that is controlled primarily by the calciotropic hormones. To maintain the Ca(2+) balance, the kidney must excrete the same amount of Ca(2+) that the small intestine absorbs. This is accomplished by a combination of filtration of Ca(2+) across the glomeruli and subsequent reabsorption of the filtered Ca(2+) along the renal tubules. Bone turnover is a continuous process involving both resorption of existing bone and deposition of new bone. The above-mentioned Ca(2+) fluxes are stimulated by the synergistic actions of active vitamin D (1,25-dihydroxyvitamin D(3)) and parathyroid hormone. Until recently, the mechanism by which Ca(2+) enter the absorptive epithelia was unknown. A major breakthrough in completing the molecular details of these pathways was the identification of the epithelial Ca(2+) channel family consisting of two members: TRPV5 and TRPV6. Functional analysis indicated that these Ca(2+) channels constitute the rate-limiting step in Ca(2+)-transporting epithelia. They form the prime target for hormonal control of the active Ca(2+) flux from the intestinal lumen or urine space to the blood compartment. This review describes the characteristics of epithelial Ca(2+) transport in general and highlights in particular the distinctive features and the physiological relevance of the new epithelial Ca(2+) channels accumulating in a comprehensive model for epithelial Ca(2+) absorption.

Epithelial Ca2+and Mg2+Channels in Health and Disease

A near constancy of the extracellular Ca(2+) and Mg(2+) concentration is required for numerous physiologic functions at the organ, tissue, and cellular levels. This suggests that minor changes in the extracellular concentration of these divalents must be detected to allow the appropriate correction by the homeostatic systems. The maintenance of the Ca(2+) and Mg(2+) balance is controlled by the concerted action of intestinal absorption, renal excretion, and exchange with bone. After years of research, rapid progress was made recently in identification and characterization of the Ca(2+) and Mg(2+) transport proteins that contribute to the delicate balance of divalent cations. Expression-cloning approaches in combination with knockout mice models and genetic studies in families with a disturbed Mg(2+) balance revealed novel Ca(2+) and Mg(2+) gatekeeper proteins that belong to the super family of the transient receptor potential (TRP) channels. These epithelial Ca(2+) (TRPV5 and TRPV6) and Mg(2+) channels (TRPM6 and TRPM7) form prime targets for hormonal control of the active Ca(2+) and Mg(2+) flux from the urine space or intestinal lumen to the blood compartment. This review describes the characteristics of epithelial Ca(2+) and Mg(2+) transport in general and highlights in particular the distinctive features and the physiologic relevance of these new epithelial Ca(2+) and Mg(2+) channels in (patho)physiologic situations.

Evaluation and treatment of pediatric idiopathic urolithiasis-revisited

The objective of the study was to update the evaluation and treatment of idiopathic urolithiasis in children in Western society. A secondary goal was to evaluate patients' compliance with high fluid intake. Over 2 years we prospectively studied children referred to us for idiopathic urolithiasis confirmed radiographically, excluding those with secondary disorders. A metabolic urinalysis, which included calcium, citrate, uric acid, oxalate, cystine, and creatinine, was ordered in all patients. Hypercalciuric patients were first treated with a low-sodium (Na)/high-potassium (K) diet and if hypercalciuria persisted, thiazides or potassium citrate was added. Follow-up ultrasound scans were scheduled every 10-12 months. Urine specific gravity (SG) measured during clinic visits was used to assess compliance with high fluid intake. A survey was sent to pediatric urologists and nephrologists to establish a recommended maximal SG value. Thirty healthy school-aged children served as controls. There were 45 children (24 males, 21 females) aged 10.4+/-2.0 years (median 11.0) studied. Stones were retrieved and analyzed in 28 showing calcium composition in all. Urine chemistry analysis was incomplete in 3, and in the others showed hypercalciuria in 33 (78.6%), hypocitraturia in 1 (2.4%), and normal values in 8 (19.0%). Treatment of 33 hypercalciuric patients consisted of diet alone in 13, potassium citrate in 17, thiazides in 2, and potassium citrate and thiazide in 1. All 33 achieved normocalciuria, apart from 2 who remained mildly hypercalciuric on diet alone. The 12 normocalciuric children were treated by diet modification alone. Follow-up ultrasonography showed no new stones in 36 of 39 patients. In 3, new stone formation was associated with recurrence of hypercalciuria after the potassium citrate dose was lowered or discontinued. Upon their first clinic visit, the urine SG of stone formers (1.021+/-0.007) was significantly higher than the maximum SG recommended by 18 physicians of 1.010+/-0.003 ( P<0.001), and not different from the SG in the control group (1.018+/-0.007). Urine SG at follow-up visits was unchanged in stone formers. We therefore propose a step-wise approach in evaluating children with idiopathic urolithiasis in Western society, in which first only urine calcium is studied. Only if urine calcium is normal, should other chemistries be studied. In many hypercalciuric children, low-Na/high-K diet alone is effective, while in most others the addition of potassium citrate is well tolerated, normalizes calciuria, and protects against new stone formation. Children rarely comply with the recommendation of high fluid intake.

Renal Ca2+ wasting, hyperabsorption, and reduced bone thickness in mice lacking TRPV5

Ca2+ ions play a fundamental role in many cellular processes, and the extracellular concentration of Ca2+ is kept under strict control to allow the proper physiological functions to take place. The kidney, small intestine, and bone determine the Ca2+ flux to the extracellular Ca2+ pool in a concerted fashion. Transient receptor potential (TRP) cation channel subfamily V, members 5 and 6 (TRPV5 and TRPV6) have recently been postulated to be the molecular gatekeepers facilitating Ca2+ influx in these tissues and are members of the TRP family, which mediates diverse biological effects ranging from pain perception to male aggression. Genetic ablation of TRPV5 in the mouse allowed us to investigate the function of this novel Ca2+ channel in maintaining the Ca2+ balance. Here, we demonstrate that mice lacking TRPV5 display diminished active Ca2+ reabsorption despite enhanced vitamin D levels, causing severe hypercalciuria. In vivo micropuncture experiments demonstrated that Ca2+ reabsorption was malfunctioning within the early part of the distal convolution, exactly where TRPV5 is localized. In addition, compensatory hyperabsorption of dietary Ca2+ was measured in TRPV5 knockout mice. Furthermore, the knockout mice exhibited significant disturbances in bone structure, including reduced trabecular and cortical bone thickness. These data demonstrate the key function of TRPV5 in active Ca2+ reabsorption and its essential role in the Ca2+ homeostasis.

24-h hydration status: parameters, epidemiology and recommendations

Hydration of individuals and groups is characterised by comparing actual urine osmolality (Uosm) with maximum Uosm. Data of actual, maximum and minimum Uosm in infants, children and adults and its major influencing factors are reviewed. There are remarkable ontogenetic, individual and cultural differences in Uosm. In the foetus and the breast-fed infant Uosm is much lower than plasma osmolality, whereas in children and adults it is usually much higher. Individuals and groups may show long-term differences in Uosm. In industrialised countries, the gender difference of Uosm is common. There are large intercultural differences of mean 24-h Uosm ranging from 860 mosm/kg in Germany, 649 mosm/kg in USA to 392 mosm/kg in Poland. A new physiologically based concept called 'free-water reserve' quantifies differences in 24-h euhydration. In 189 boys of the DONALD Study aged 4.0-6.9 y, median urine volume was 497 ml/24-h and median Uosm 809 mosm/kg. Considering mean-2 s.d. of actual maximum 24-h Uosm of 830 mosm/kg as upper level of euhydration and physiological criterion of adequate hydration in these boys, median free-water reserve was 11 ml/24-h. Based on median total water intake of 1310 ml/24-h and the third percentile of free-water volume of -156 ml/24-h, adequate total water intake was 1466 ml/24-h or 1.01 ml/kcal. Data of Uosm in 24-h urine samples and corresponding free-water reserve values of homogeneous groups of healthy subjects from all over the world might be useful parameters in epidemiology to investigate the health effects of different levels of 24-h euhydration.