Chronic kidney disease mineral and bone disorder in children

Chronic Kidney Disease and Growth Failure in Children

Chronic kidney disease (CKD) is a significant challenge for pediatric endocrinologists, as children with CKD may present a variety of endocrine complications. Growth failure is common in CKD, and its severity is correlated with the degree of renal insufficiency. Management strategies include addressing reversible comorbidities, optimizing nutrition, and ensuring metabolic control. Kidney replacement therapy, including transplantation, determines a significant improvement in growth. According to a recent Consensus Statement, children with CKD stage 3-or on dialysis older >6 months-are eligible for treatment with recombinant growth hormone (rGH) in the case of persistent growth failure. Treatment with rGH may be considered for those with height between the 3rd and 10th percentile and persistent growth deceleration. In children who received kidney transplantation but continue to experience growth failure, initiation of GH therapy is recommended one year post-transplantation if spontaneous catch-up growth does not occur and steroid-free immunosuppression is not an option. In children with CKD, due to nephropathic cystinosis and persistent growth failure, GH therapy should be considered at all stages of CKD. Potential adverse effects and benefits must be regularly assessed during therapy. Treatment with GH is safe in children with CKD. However, its general efficacy is still controversial. All possible problems with a negative impact on growth should be timely addressed and resolved, whenever possible with a personalized approach to the patient. GH therapy may be useful in promoting catch-up growth in children with residual growth potential. Future research should focus on refining effective therapeutic strategies and establishing consensus guidelines to optimize growth outcomes in this population.

Safety of cinacalcet in children and adolescents with chronic kidney disease-mineral bone disorder: systematic review and proportional meta-analysis of case series

BACKGROUND

Mineral and bone disease in children with chronic kidney disease can cause abnormalities in calcium, phosphorus, parathyroid hormone, and vitamin D and when left untreated can result in impaired growth, bone deformities, fractures, and vascular calcification. Cinacalcet is a calcimimetic widely used as a therapy to reduce parathyroid hormone levels in the adult population, with hypocalcemia among its side effects. The analysis of safety in the pediatric population is questioned due to the scarcity of randomized clinical trials in this group.

OBJECTIVE

To assess the onset of symptomatic hypocalcemia or other adverse events (serious or non-serious) with the use of cinacalcet in children and adolescents with mineral and bone disorder in chronic kidney disease.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

The bibliographic search identified 2699 references from 1927 to August/2023 (57 LILACS, 44 Web of Science, 686 PubMed, 131 Cochrane, 1246 Scopus, 535 Embase). Four references were added from the bibliography of articles found and 12 references from the gray literature (Clinical Trials). Of the 77 studies analyzed in full, 68 were excluded because they did not meet the following criteria: population, types of studies, medication, publication types and 1 article that did not present results (gray literature).

PARTICIPANTS AND INTERVENTIONS

There were 149 patients aged 0-18 years old with Chronic Kidney Disease and mineral bone disorder who received cinacalcet.

STUDY APPRAISAL AND SYNTHESIS METHODS

Nine eligible studies were examined for study type, size, intervention, and reported outcomes.

RESULTS

There was an incidence of 0.2% of fatal adverse events and 16% of serious adverse events (p < 0.01 and I2 = 69%), in addition to 10.7% of hypocalcemia, totaling 45.7% of total adverse events.

LIMITATIONS

There was a bias in demographic information and clinical characteristics of patients in about 50% of the studies and the majority of the studies were case series.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

If used in the pediatric population, the calcimimetic cinacalcet should be carefully monitored for serum calcium levels and attention to possible adverse events, especially in children under 50 months.

SYSTEMATIC REVIEW REGISTRATION NUMBER (PROSPERO REGISTER)

CRD42019132809.

Chronic kidney disease mineral bone disorder in childhood and young adulthood: a 'growing' understanding

Chronic kidney disease (CKD) mineral and bone disorder (MBD) comprises a triad of biochemical abnormalities (of calcium, phosphate, parathyroid hormone and vitamin D), bone abnormalities (turnover, mineralization and growth) and extra-skeletal calcification. Mineral dysregulation leads to bone demineralization causing bone pain and an increased fracture risk compared to healthy peers. Vascular calcification, with hydroxyapatite deposition in the vessel wall, is a part of the CKD-MBD spectrum and, in turn, leads to vascular stiffness, left ventricular hypertrophy and a very high cardiovascular mortality risk. While the growing bone requires calcium, excess calcium can deposit in the vessels, such that the intake of calcium, calcium- containing medications and high calcium dialysate need to be carefully regulated. Normal physiological bone mineralization continues into the third decade of life, many years beyond the rapid growth in childhood and adolescence, implying that skeletal calcium requirements are much higher in younger people compared to the elderly. Much of the research into the link between bone (de)mineralization and vascular calcification in CKD has been performed in older adults and these data must not be extrapolated to children or younger adults. In this article, we explore the physiological changes in bone turnover and mineralization in children and young adults, the pathophysiology of mineral bone disease in CKD and a potential link between bone demineralization and vascular calcification.

Mineral bone disorder in children with chronic kidney disease: Data from the KNOW-Ped CKD (Korean cohort study for outcome in patients with pediatric chronic kidney disease) study

BACKGROUND

Children with chronic kidney disease (CKD) are at high risk of mineral bone disorder (MBD), which leads to fractures, growth retardation, and cardiovascular disease. We aimed to comprehensively understand the relationship between renal function and factors related to MBD and evaluate the prevalence and distribution characteristics of MBD, specifically among Korean patients from the KNOW-PedCKD cohort.

METHODS

From the baseline data of the KNOW-PedCKD cohort, we examined the prevalence and distribution of MBD in 431 Korean pediatric CKD patients, including the level of corrected total calcium, serum phosphate, serum alkaline phosphatase, serum intact parathyroid hormone (iPTH), fibroblast growth factor 23 (FGF-23), serum vitamin D, fractional excretion of phosphate (FEP), and bone densitometry Z-scores.

RESULTS

The median serum calcium level remained relatively normal regardless of the CKD stage. The levels of 1,25-dihydroxy vitamin D, urine calcium-to-creatinine ratio, and bone densitometry Z-score significantly decreased with advancing CKD stage, while those of serum phosphate, FGF-23, and FEP significantly increased with CKD stage. The prevalence of hyperphosphatemia (17.4%, 23.7%, and 41.2% from CKD stages 3b, 4, and 5, respectively) and hyperparathyroidism (37.3%, 57.4%, 55.3%, and 52.9% from CKD stages 3a, 3b, 4, and 5, respectively) significantly increased with the CKD stage. Prescriptions of medications, such as calcium supplements (39.1%, 42.1%, 82.4%), phosphate binders (39.1%, 43.4%, 82.4%), and active vitamin D (21.7%, 44.7%, and 64.7%) significantly increased with CKD stage 3b, 4, and 5, respectively.

CONCLUSIONS

The results demonstrated the prevalence and relationship of abnormal mineral metabolism and bone growth according to CKD stage in Korean pediatric CKD patients for the first time.

Serum PTH, PTH1R/ATF4 pathway, and the sRANKL/OPG system in bone as a new link between bone growth, cross-sectional geometry, and strength in young rats with experimental chronic kidney disease

The progression of chronic kidney disease (CKD) in children is associated with deregulated parathyroid hormone (PTH), growth retardation, and low bone accrual. PTH can cause both catabolic and anabolic impact on bone, and the activating transcription factor 4 (ATF4), a downstream target gene of PTH, is related to its anabolic effect. Osteoprotegerin (OPG) and receptor activator of NF-κB ligand (RANKL) are PTH-dependent cytokines, which may play an important role in the regulation of bone remodeling. This study aimed to evaluate the impact of endogenous PTH and the bone RANKL/OPG system on bone growth, cross-sectional geometry and strength utilizing young, nephrectomized rats. The parameters of cross-sectional geometry were significantly elevated in rats with CKD during the three-month experimental period compared with the controls, and they were strongly associated with serum PTH levels and the expression of parathyroid hormone 1 receptor (PTH1R)/ATF4 genes in bone. Low bone soluble RANKL (sRANKL) levels and sRANKL/OPG ratios were also positively correlated with cross-sectional bone geometry and femoral length. Moreover, the analyzed geometric parameters were strongly related to the biomechanical properties of femoral diaphysis. In summary, the mild increase in endogenous PTH, its anabolic PTH1R/ATF4 axis and PTH-dependent alterations in the bone RANKL/OPG system may be one of the possible mechanisms responsible for the favorable impact on bone growth, cross-sectional geometry and strength in young rats with experimental CKD.

Bone evaluation in paediatric chronic kidney disease: clinical practice points from the European Society for Paediatric Nephrology CKD-MBD and Dialysis working groups and CKD-MBD working group of the ERA-EDTA

Mineral and bone disorder (MBD) is widely prevalent in children with chronic kidney disease (CKD) and is associated with significant morbidity. CKD may cause disturbances in bone remodelling/modelling, which are more pronounced in the growing skeleton, manifesting as short stature, bone pain and deformities, fractures, slipped epiphyses and ectopic calcifications. Although assessment of bone health is a key element in the clinical care of children with CKD, it remains a major challenge for physicians. On the one hand, bone biopsy with histomorphometry is the gold standard for assessing bone health, but it is expensive, invasive and requires expertise in the interpretation of bone histology. On the other hand, currently available non-invasive measures, including dual-energy X-ray absorptiometry and biomarkers of bone formation/resorption, are affected by growth and pubertal status and have limited sensitivity and specificity in predicting changes in bone turnover and mineralization. In the absence of high-quality evidence, there are wide variations in clinical practice in the diagnosis and management of CKD-MBD in childhood. We present clinical practice points (CPPs) on the assessment of bone disease in children with CKD Stages 2-5 and on dialysis based on the best available evidence and consensus of experts from the CKD-MBD and Dialysis working groups of the European Society for Paediatric Nephrology and the CKD-MBD working group of the European Renal Association-European Dialysis and Transplant Association. These CPPs should be carefully considered by treating physicians and adapted to individual patients' needs as appropriate. Further areas for research are suggested.

Short stature in advanced pediatric CKD is associated with faster time to reduced kidney function after transplant

BACKGROUND

Among children who receive a kidney transplant, short stature is associated with a more complicated post-transplant course and increased mortality. Short stature prior to transplant may reflect the accumulated risk of multiple factors during chronic kidney disease (CKD); however, its relationship with post-transplant kidney function has not been well characterized.

METHODS

In the Chronic Kidney Disease in Children (CKiD) cohort restricted to children who received a kidney transplant, short stature (i.e., growth failure) was defined as age-sex-specific height < 3rd percentile. The outcome was time to estimated glomerular filtration rate (eGFR) < 45 ml/min/1.73 m² after transplant. Parametric survival models, including adjustment for disease severity, socioeconomic status (SES), and parental height by inverse probability weighting, described the relative times to eGFR< 45 ml/min/1.73 m².

RESULTS

Of 138 children (median CKD duration at transplant: 13 years), 20% (28) had short stature before the transplant. The median time to eGFR < 45 ml/min/1.73 m² after kidney transplantation was 6.6 years and those with short stature had a significantly faster time to the poor outcome (log-rank p value 0.004). Children with short stature tended to have lower SES, nephrotic proteinuria, higher blood pressure, and lower mid-parental height before transplant. After adjusting for these variables, children with growth failure had 40% shorter time to eGFR < 45 ml/min/1.73 m² than those with normal stature (relative time 0.60, 95%CI 0.32, 1.03).

CONCLUSIONS

Short stature was associated with a faster time to low kidney function after transplant. SES, disease severity, and parental height partially explained the association. Clinicians should be aware of the implications of growth failure on the outcome of this unique population, while continued attempts are made to define modifiable factors that contribute to this association.

Pathogenesis and treatment of electrolyte problems post transplant

PURPOSE OF REVIEW

Electrolyte abnormalities posttransplant are common occurrences that can have significant short-term and long-term effects on graft outcome and patient quality of life. Understanding the pathophysiology of these electrolyte derangements can help guide management to optimize bone health and minimize cardiovascular disease. This review explores the pathogenesis of the most common postrenal transplant electrolytes abnormalities as well as current treatment options.

RECENT FINDINGS

Clarifications of the role of FGF-23 has improved our understanding of posttransplant bone disease in addition to the known roles of hyperparathyroidism and vitamin D. The mechanisms of renal electrolyte wasting by immunosuppressive agents give insight into potential treatment options for hyperkalemia and hypomagnesemia.

SUMMARY

Understanding the pathogenesis of the common electrolyte abnormalities found post renal transplant may lead to targeted treatment options that in turn may improve transplant complications. Further studies are required to evaluate the effects on long-term outcomes of renal allografts.

RANKL/OPG system regulation by endogenous PTH and PTH1R/ATF4 axis in bone: Implications for bone accrual and strength in growing rats with mild uremia

Osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL), and parathyroid hormone (PTH) play a central role in the regulation of bone turnover in chronic kidney disease (CKD), but their influence on bone mineral density (BMD) and strength remains unclear, particularly in children. We studied the clinical significance of OPG and RANKL in relation to PTH, femur weight, BMD, and bone biomechanical properties in growing rats after one month (CKD-1) and three months (CKD-3) of surgically-induced mild CKD. Gene expression of parathyroid hormone 1 receptor (PTH1R) and activating transcription factor 4 (ATF4), major regulators of anabolic PTH response in bone, was also determined. Serum PTH and bone PTH1R/ATF4 expression was elevated in CKD-3 compared with other groups, and it positively correlated with femur weight, BMD, and the biomechanical properties of the femoral diaphysis reflecting cortical bone strength. In contrast, bone RANKL/OPG ratios were decreased in CKD-3 rats compared with other groups, and they were inversely correlated with PTH and the other abovementioned bone parameters. However, the PTH-PTH1R-ATF4 axis exerted an unfavorable effect on the biomechanical properties of the femoral neck. In conclusion, this study showed for the first time an inverse association between serum PTH and the bone RANKL/OPG system in growing rats with mild CKD. A decrease in the RANKL/OPG ratio, associated with PTH-dependent activation of the anabolic PTH1R/ATF4 pathway, seems to be responsible for the unexpected, beneficial effect of PTH on cortical bone accrual and strength. Simultaneously, impaired biomechanical properties of the femoral neck were observed, making this bone site more susceptible to fractures.

Efficacy and safety of sevelamer carbonate in hyperphosphatemic pediatric patients with chronic kidney disease

BACKGROUND

Treatment for hyperphosphatemia in chronic kidney disease (CKD) involves dietary control of phosphorus intake, dialysis, and treatment with oral phosphate binders, none of which were approved by the Federal Food and Drug Administration in pediatric patients at the time of this study.

METHODS

This was a phase 2, multicenter study (NCT01574326) with a 2-week, randomized, placebo-controlled, fixed-dose period (FDP) followed by a 6-month, single-arm, open-label, dose-titration period (DTP), with the aim to evaluate the safety and efficacy of sevelamer carbonate (SC) in hyperphosphatemic pediatric patients with CKD. Following a 2-4 week screening phase, pediatric patients with a serum phosphorus level higher than age-appropriate levels were randomized to receive either SC or placebo as powder/tablets in 0.4-1.6 g doses, based on body surface area. The primary efficacy outcome was the change in serum phosphorus from baseline to end of the FDP in the SC versus placebo arms (analysis of covariance). The secondary outcome was mean change in serum phosphorus from baseline to end of DTP by treatment group and overall. Treatment-emergent/serious adverse events (AEs) were recorded.

RESULTS

Of 101 enrolled patients (29 centers), 66 completed the study. The majority of patients were adolescents (74%; mean age 14.1 years) and on dialysis (77%). Renal transplant was the main reason for discontinuation. SC significantly reduced serum phosphorus from baseline levels (7.16 mg/dL) during the FDP compared to placebo (least square mean difference - 0.90 mg/dL, p = 0.001) and during the DTP (- 1.18 mg/dL, p < 0.0001). The safety and tolerability of SC and placebo were similar during the FDP, with patients in both groups reporting mild/moderate gastrointestinal AEs during the DTP.

CONCLUSIONS

Sevelamer carbonate significantly lowered serum phosphorus levels in hyperphosphatemic children with CKD, with no serious safety concerns identified.

Efficacy and safety of paricalcitol in children with stages 3 to 5 chronic kidney disease

BACKGROUND

Elevated intact parathyroid hormone (iPTH) levels can contribute to morbidity and mortality in children with chronic kidney disease (CKD). We evaluated the pharmacokinetics, efficacy, and safety of oral paricalcitol in reducing iPTH levels in children with stages 3-5 CKD.

METHODS

Children aged 10-16 years with stages 3-5 CKD were enrolled in two phase 3 studies. The stage 3/4 CKD study characterized paricalcitol pharmacokinetics and compared the efficacy and safety of paricalcitol with placebo followed by an open-label period. The stage 5 CKD study evaluated the efficacy and safety of paricalcitol (no comparator) in children with stage 5 CKD undergoing dialysis.

RESULTS

In the stage 3/4 CKD study, mean peak plasma concentration and area under the time curve from zero to infinity were 0.13 ng/mL and 2.87 ng•h/((or ng×h/))mL, respectively, for 12 children who received 3 μg paricalcitol. Thirty-six children were randomized to paricalcitol or placebo; 27.8% of the paricalcitol group achieved two consecutive iPTH reductions of ≥30% from baseline versus none of the placebo group (P = 0.045). Adverse events were higher in children who received placebo than in those administered paricalcitol during the double-blind treatment (88.9 vs. 38.9%; P = 0.005). In the stage 5 CKD study, eight children (61.5%) had two consecutive iPTH reductions of ≥30% from baseline, and five (38.5%) had two consecutive iPTH values of between 150 and 300 pg/mL. Clinically meaningful hypercalcemia occurred in 21% of children.

CONCLUSIONS

Oral paricalcitol in children aged 10-16 years with stages 3-5 CKD reduced iPTH levels and the treatment was well tolerated. Results support an initiating dose of 1 μg paricalcitol 3 times weekly in children aged 10-16 years.

Association of bone mineral density with biochemical markers of bone turnover in hemodialysis children

Introduction: Although some descriptive and cross-sectional studies have been reported about bone mass in chronic kidney disease (CKD) children, only a few studies investigated markers of bone turnover and the bone mass measurements.

Objectives: The aim of this study was to evaluate the association between bone mineral density (BMD) and biochemical markers of bone turnover in hemodialysis (HD) children.

Patients and Methods: The children who had received dialysis for at least the preceding 6‐month were included. BMD was measured for total body, the lumbar spine and the femoral neck and the blood samples were tested to assess biochemical bone turnover markers.

Results: The study group was comprised of 27 patients with CKD, 9 males (33%) and 18 females (67%) with the mean±SD age of the subjects 14.9±4.5 years. Positive significant correlations of parathyroid hormone (PTH) with total body bone densitometry Z-score, lumbar spine and femoral neck Z-score(r=0.43, P=0.06; r=0.41, P=0.08 and r=0.45, P=0.05, respectively) was noted. In addition, positive significant correlations calcium and total body, lumbar spine and femoral neck Z-score (r=0.52, P=0.02; r=0.28, P=0.23 and r=0.36, P=0.12, respectively) was seen. Interestingly, a positive significant correlation between alkaline phosphatase (ALP) and lumbar spine Z-score was found (r=0.46, P=0.04), while the correlation of this parameter with total body and femoral neck Z-score was not significant (P>0.05).

Conclusion: In our study, majority of patients with CKD had low level of BMD. In addition, lower levels of calcium (Ca), phosphorus (P), PTH and 25 (OH) vitamins D in patients with abnormal BMD Z-scores were detected.

Matrix Metalloproteinase (MMP)-9 Levels in Children on Hemodialysis: Association with MMP-9 C-1562T Gene Polymorphism and Vitamin D Levels

BACKGROUND AND OBJECTIVES

Data concerning the concentration of matrix metalloproteinase-9 (MMP-9) and its functional polymorphisms in chronic kidney diseases (CKD) are conflicting. The present study aimed to evaluate the levels of MMP-9in children with end stage renal diseases (ESRD) on hemodialysis (HD) and to explore its association with MMP-9 polymorphism and vitamin D levels as an important risk factors for cardiovascular diseases (CVD).

METHODS

We studied 55 children with ESRD on hemodialysis and 18 healthy children served as controls. MMP-9 and vitamin D levels were measured by ELISA in serum of all patients and controls. Genotypes for MMP-9 polymorphism(C^-1562T) were determined by RFLP for only 28 of the patients and all the controls.

RESULTS

There were insignificantly reduced MMP-9levels of patients vs. controls, however, there was significant increase in MMP-9 levels associated with CC genotypes for(C^-1562T) polymorphism compared with CT genotype (p=0.01). We found that at MMP-9 base position-1562, the frequencies of the genotypes CC and CT in Children on HD were 71.4% and 28.6% respectively while all our controls were of the CC genotype. The alleles frequencies of C and T in patients were 85.7% and 14.29% as compared to 100% and 0%, respectively in the controls. Significant decrease in vitamin D was observed in children on HD versus that in controls (p=0.008). Serum MMP9 levels and age were variables that were independently associated with CVD.

CONCLUSIONS

MMP9 genetic polymorphism (C^-1562T) affects MMP9alterations in ESRD children on HD and vitamin D deficiency is common in our HD pediatric patients who require attention in accordance with current practice guidelines. They probably require supplementation with higher doses of cholecalciferol.

Oral Manifestations of Chronic Kidney Disease and Renal Secondary Hyperparathyroidism: A Comparative Review

Recent epidemiological studies have demonstrated that significant associations exist between oral disease and diseases involving non-oral tissues. Occasionally, the roles may be reversed and the oral cavity can be severely affected by systemic disease originating in another part of the body. Renal secondary hyperparathyroidism is a common endocrinopathy that occurs as a consequence of chronic azotemic kidney disease. Renal osteodystrophy, the most dramatic clinical consequence of renal secondary hyperparathyroidism is uncommon, but can result in demineralization of maxillofacial bones, loosening of teeth, and pathological jaw fractures. The purpose of this report is to update the current understanding of the pathophysiology of this endocrine disease and to compare the oral manifestations of renal secondary hyperparathyroidism in humans and companion animals. A 50-year review of the veterinary literature was undertaken to examine the clinical presentation of renal osteodystrophy in dogs, and to determine what clinical consequences of renal secondary hyperparathyroidism have been reported in domestic cats.

Association between bone stiffness and nutritional biomarkers combined with weight-bearing exercise, physical activity, and sedentary time in preadolescent children. A case-control study

Physical activity (PA) and micronutrients such as calcium (Ca), vitamin D (25OHD), and phosphate (PO) are important determinants of skeletal development. This case-control study examined the association of these nutritional biomarkers and different PA behaviours, such as habitual PA, weight-bearing exercise (WBE) and sedentary time (SED) with bone stiffness (SI) in 1819 2-9-year-old children from the IDEFICS study (2007-2008). SI was measured on the calcaneus using quantitative ultrasound. Serum and urine Ca and PO and serum 25OHD were determined. Children's sports activities were reported by parents using a standardised questionnaire. A subsample of 1089 children had accelerometer-based PA data (counts per minute, cpm). Moderate-to-vigorous PA (MVPA) and SED were estimated. Children with poor SI (below the 15th age-/sex-/height-specific percentile) were defined as cases (N=603). Randomly selected controls (N=1216) were matched by age, sex, and country. Odds ratios (OR) for poor SI were calculated by conditional logistic regression for all biomarkers and PA behaviour variables separately and combined (expressed as tertiles and dichotomised variables, respectively). ORs were adjusted for fat-free mass, dairy product consumption, and daylight duration. We observed increased ORs for no sports (OR=1.39, p<0.05), PA levels below 524 cpm (OR=1.85, p<0.05) and MVPA below 4.2% a day (OR=1.69, p<0.05) compared to WBE, high PA levels (<688 cpm) and high MVPA (6.7%), respectively. SED was not associated with SI. ORs were moderately elevated for low serum Ca and 25OHD. However, biomarkers were not statistically significantly associated with SI and did not modify the association between PA behaviours and SI. Although nutritional biomarkers appear to play a minor role compared to the osteogenic effect of PA and WBE, it is noteworthy that the highest risk for poor SI was observed for no sports or low MVPA combined with lower serum Ca (<2.5 mmol/l) or lower 25OHD (<43.0 nmol/l).

Fractures Related to Metabolic Bone Disease in Children with Congenital Heart Disease

OBJECTIVE

Critically ill children with congenital heart disease (CHD) are at risk for metabolic bone disease (MBD) and bone fractures. Our objective was to characterize a cohort of CHD patients with fractures and describe a Fragile Bone Protocol (FBP) developed to reduce fractures.

DESIGN/SETTING

Patients who developed fractures in the Cardiac Intensive Care Unit (CICU) of Boston Children's Hospital from 3/2008 to 6/2014 were identified via quality improvement and radiology databases. The FBP (initiated July 2011) systematically identifies patients at risk for MBD and prescribes special handling precautions.

RESULTS

Twenty-three fractures were identified in 15 children. Median age at fracture identification was 6.2 months, with a median duration of hospitalization before fracture diagnosis of 2.7 months. Six patients (40%) had single ventricle CHD. Hyperparathyroidism and low 25-OH vitamin D levels were present in 77% and 40% of those tested, respectively. Compared with patients not diagnosed with fractures, fracture patients had increased exposure to possible risk factors for MBD and had elevated parathyroid and decreased calcitriol levels.Six patients (40%) did not survive to hospital discharge, compared with an overall CICU mortality rate of 2.6% (P < .01). The fracture case rate before implementation of the FBP was 2.6 cases/1000 admissions and was 0.7/1000 after implementation of the FBP (P = .04).

CONCLUSIONS

Critically ill CHD patients are at risk for fractures. They represent a complex group who frequently has hyperparathyroidism and decreased calcitriol levels, and each may predispose to fractures. FBPs consisting of identification and careful patient handling should be considered in at-risk patients.

[Online hemodiafiltration in children and hypoparathyroidism: a single-centre series of cases]

BACKGROUND

Due to technical requirements and cost, hemodiafiltration (HDF) is not widely used in pediatrics. We have been using online HDF (oHDF) since 2009 and we observed low parathyroid hormone (PTH) levels despite the accurate management of CKD-MBD.

METHODS

We reviewed the medical charts and parameters of mineral metabolism assessed on a before/after session basis in the 6 children undergoing chronic oHDF in our centre.

RESULTS

We observed low (<80pg/mL) PTH levels in all 6 patients and very low (<45pg/mL) PTH levels in 5, two of them presenting with pathological fractures. These low PTH levels were reversed after decreasing calcium concentration to 1.25 mmol/L in the dialysate, suggesting that high-efficiency oHDF may expose children to calcium during sessions in a too important amount when using 1.5 mmol/L dialysates. Last, C-terminal FGF23 levels before sessions were relatively low (<1600RU/mL), with a 32% clearance by oHDF.

CONCLUSION

PTH levels should be closely monitored in pediatric oHDF and solutions with a calcium concentration of 1.25 mmol/L should be used as first line in these patients.

Defective bone microstructure in hydronephrotic mice: a histomorphometric study in ICR/Mlac-hydro mice

Chronic renal impairment can lead to bone deterioration and abnormal bone morphology, but whether hydronephrosis is associated with bone loss remains unclear. Herein, we aimed to use computer-assisted bone histomorphometric technique to investigate microstructural bone changes in Imprinting Control Region (ICR) mice with a spontaneous mutation that was associated with bilateral nonobstructive hydronephrosis (ICR/Mlac-hydro). The results showed that 8-week-old ICR/Mlac-hydro mice manifested decreases in trabecular bone number and thickness, and an increased trabecular separation, thereby leading to a reduction in trabecular bone volume compared with the wild-type mice. Furthermore, histomorphometric parameters related to both bone resorption and formation, that is, eroded surface, osteoclast surface, and osteoblast surface, were much lower in ICR/Mlac-hydro mice than in the wild type. A decrease in moment of inertia was found in ICR/Mlac-hydro mice, indicating a decrease in bone strength. In conclusion, ICR/Mlac-hydro mice exhibited trabecular bone loss, presumably caused by marked decreases in both osteoblast and osteoclast activities, which together reflected abnormally low bone turnover. Thus, this mouse strain appeared to be a valuable model for studying the hydronephrosis-associated bone disease.

Clinical and etiological profile of refractory rickets from western India

OBJECTIVE

To present clinical and etiological profile of refractory rickets from Mumbai.

METHODS

Case records of 36 patients presenting over 2½ y with refractory rickets were evaluated with respect to clinical presentation, biochemical, radiological features and where needed, ophthalmological examination, ultrasonography and special tests on blood and urine.

RESULTS

Twenty three (63 %) patients had renal tubular acidosis (RTA)-distal RTA in 20 and proximal RTA in 3 patients; 5 (14 %) had vitamin D dependent rickets (VDDR I in 2 and VDDR II in 3 patients), 4 (11 %) had chronic renal failure (CRF) and 2 each (6 %) had hypophosphatemic rickets and chronic liver disease as cause of refractory rickets. A significant proportion of patients with RTA and VDDR showed skeletal changes of rickets in the first 2 y of life, while those with hypophosphatemic rickets presented later. Patients with hypophosphatemic rickets had predominant involvement of lower limbs, normal blood calcium and PTH levels and phosphorus leak in urine. All patients with RTA presented with failure to thrive, polyuria and marked rickets; blood alkaline phosphatase levels being normal in almost 50 % patients. Three (75 %) patients with rickets due to CRF had GFR < 30 ml/min/1.73 m(2) and hyperphosphatemia. Patients with cirrhosis due to biliary atresia had rickets inspite of taking high dose of vitamin D orally.

CONCLUSIONS

Refractory rickets is a disorder of multiple etiologies; a good history and clinical examination supplemented with appropriate investigations helps to determine its cause.

[Relationship between glomerular filtration rate, uric acid, and parathyroid hormone in children]

INTRODUCTION

Parathyroid hormone (PTH) and uric acid (UA) levels increase early during chronic kidney disease (CKD). The objective of this study was to evaluate the relationship between these two parameters at different stages of pediatric CKD.

PATIENTS AND METHODS

One hundred patients (range, 5-18 years) were included in this retrospective study: they had undergone renal exploration with a direct measurement of the glomerular filtration rate (GFR) using the reference standard (i.e., inulin clearance, Cin) and presented with increased circulating levels of PTH and/or UA.

RESULTS

GFR was normal in 39% of patients, with UA increased in 44% and PTH in 75% of them. Interestingly, 29% of the children with increased PTH levels had a strictly normal GFR (i.e., above 90 mL/min/1.73 m(2)). An inverse association was found between UA and GFR (r=-0.452, P ≤ 0.0001) as well as between PTH and GFR (r=-0.226, P=0.024). The same negative relationships were found between UA and PTH (r=-0.266, P=0.007), and between UA and the phosphate reabsorption rate (r=-0.415, P<0.001).

DISCUSSION

Since hyperuricemia was found at all stages of CKD, an early silent tubular impairment can be discussed to explain these findings. The early increase in PTH levels during CKD has not been described by all authors, with North American studies describing rather late increased PTH levels during CKD. Prospective studies are required to confirm these data and evaluate the role of UA in the pathophysiology of the mineral disorders observed during CKD.

Searching the optimal PTH target range in children undergoing peritoneal dialysis: new insights from international cohort studies

The treatment of the mineral and bone disorder associated with chronic kidney disease (CKD-MBD) remains a major challenge in pediatric patients. The principal aims of therapeutic measures are not only to prevent the debilitating skeletal complications and to achieve normal growth but also to preserve long-term cardiovascular health. Serum parathyroid hormone (PTH) levels are used as a surrogate parameter of bone turnover. Whereas it is generally accepted that serum calcium and phosphate levels should be kept within the range for age, current pediatric consensus guidelines differ markedly with respect to the optimal PTH target range and operate on a limited evidence base. Recently, the International Pediatric Dialysis Network (IPPN) established a global registry collecting detailed clinical and biochemical information, including data relevant to CKD-MBD in children on chronic peritoneal dialysis (PD). This review highlights the current evidence basis regarding the optimal PTH target range in pediatric CKD patients, and re-assesses the current guidelines in view of the outcome data collected by the IPPN registry. Based on a comprehensive evaluation of CKD-MBD outcome measures in this global patient cohort, a PTH target range of 1.7-3 times the upper limit of normal (i.e. 100-200 pg/ml) appears reasonable in children undergoing chronic PD.

Changes in bone matrix mineralization after growth hormone treatment in children and adolescents with chronic kidney failure treated by dialysis: a paired biopsy study

BACKGROUND

Patients with chronic kidney disease (CKD) develop renal osteodystrophy with alterations in bone turnover, mineralization, and volume (TMV). A specific skeletal complication in children is growth impairment, which currently is treated by recombinant human growth hormone (rhGH). The effects on bone material properties are poorly understood. This study assesses the effects of rhGH treatment on bone matrix mineralization.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

18 short children and adolescents (aged 3.6-16 years) with CKD on dialysis therapy.

PREDICTOR

rhGH treatment for 1 year.

OUTCOMES

Tetracycline-labeled bone biopsy classified according to the TMV system.

MEASUREMENTS

Bone mineralization density distribution (BMDD) was evaluated by quantitative backscattered electron imaging in trabecular and cortical compartments. Additional data for patients' height and biochemical bone serum parameters were obtained.

RESULTS

Prior to rhGH treatment, our cohort showed low bone turnover and high mineralization densities versus reference data: Ca(mean) (weighted mean calcium content) in cancellous bone, +3.3% (P = 0.04); Ca(mean) in cortical bone, +6.7% (P < 0.001); Ca(peak) (mode of the BMDD) in cancellous bone, +5.0% (P < 0.001); Ca(peak) in cortical bone, +8.2% (P < 0.001); Ca(width) (heterogeneity in mineralization), no significant difference for cancellous (P = 0.2) and cortical (P = 0.1) bone; Ca(high) (portion of fully mineralized bone) in cancellous bone, 5-fold greater (P < 0.001); Ca(high) in cortical bone, 14-fold greater (P < 0.001); Ca(low) (portion of low mineralized bone) in cancellous bone, +23.9% (P = 0.02); Ca(low) in cortical bone, -22.2% (P = 0.05). After rhGH treatment, height increased by 9.1 cm (P < 0.001) and bone turnover indices to normal values or beyond. Matrix mineralization was lesser and more heterogeneous compared to baseline: Ca(width) for cancellous bone, +15.3% (P < 0.001); Ca(width) for cortical bone, +34.1% (P < 0.001). Ca(mean), Ca(peak), and Ca(high) for cancellous bone and Ca(mean) and Ca(peak) for cortical bone were no longer significantly different from reference data. Ca(high) for cortical bone dramatically decreased after treatment but was still substantially greater than reference data.

LIMITATIONS

Low case number per TMV subgroup, no measurements of fibroblast growth factor 23.

CONCLUSIONS

Children and adolescents with CKD and growth deficiency are at risk of having low bone turnover. rhGH treatment improves height and concomitantly bone modeling/remodeling, which appears beneficial for bone matrix mineralization.

Rickets: Part II

This is the continuation of a two-part review of rickets. This part emphasizes the specific pathophysiology, clinical features, pathoanatomy and radiographic findings of vitamin D deficiency rickets. Other forms of rickets, differential diagnostic considerations and the potential relationship between low levels of vitamin D metabolites and unexplained fractures in infants are also discussed.

Intima media thickness in children undergoing dialysis

BACKGROUND

Uremic vasculopathy, including vascular calcification, increases the risk for cardiovascular disease and mortality in chronic kidney disease (CKD) patients. We have investigated the prevalence and factors associated with vasculopathy in children undergoing peritoneal dialysis (PD) or hemodialysis (HD) in a single center.

METHODS

Common carotid intima media thickness (cIMT) and its relation with demographics, biochemical parameters and medication was analyzed in 60 patients (mean age 12.9 ± 3.4 years; 27 girls) treated with PD (n = 31) or HD (n = 29) for 34 ± 34 months. Patients were divided into two groups: normal cIMT and increased cIMT.

RESULTS

Mean levels of calcium, phosphate and calcium/phosphate product were in the normal range, the but parathyroid hormone level, 729 ± 670 pg/mL, was higher than the National Kidney Foundation Kidney Disease Outcome Quality Iniative (K/DOQI) recommendations. Twenty-nine patients had increased cIMT, which was associated with time on dialysis of >2 years, hypercalcemia, higher daily dose of calcitriol and HD (vs. PD). In the multivariate analysis, accounting for time on dialysis, HD persisted as a risk for increased cIMT.

CONCLUSIONS

The prevalence of increased cIMT in children on dialysis is similar to that reported in adults with CKD and increased with time on dialysis. HD was associated with increased cIMT, independently of time on dialysis; however, the results should be interpreted with caution due to the possible impact of confounding factors. These results underline the need to monitor and, if possible, prevent and treat increased cIMT in children on dialysis.

Vitamin D status in children with chronic kidney disease

BACKGROUND

The role of vitamin D status in patients with renal insufficiency and its relation to dietary intake and parathyroid hormone (PTH) secretion is of utmost interest given the morbidity and mortality associated with the disordered mineral metabolism seen in chronic kidney disease (CKD).

METHODS

We conducted a cross-sectional study of 100 pediatric patients with a diagnosis of CKD stage 1-5 at Children's Hospital Boston, measuring blood levels of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], and parathyroid hormone and obtaining data on nutrient intake and other variables related to vitamin D status.

RESULTS

Subjects ranged in age from 6 months to 18 years, and 60 were male, 40 female. Of the 100 patients, 16 % were deficient in 25(OH)D (≤ 20 ng/mL) and another 24 % were insufficient (≤ 30 ng/mL), with 40 % in the suboptimal range. Serum 25(OH)D and dietary vitamin D intake were not correlated.

CONCLUSIONS

We found a high prevalence of hyperparathyroidism in early-stage CKD and a significant relationship between 25(OH)D and PTH regardless of calcitriol level. Our study results support the suggestion that optimization of vitamin D levels may provide additional benefit in preventing or improving hyperparathyroidism in patients with early CKD and likely remains important as an adjunctive therapy in children with advanced CKD.

The consequences of chronic kidney disease on bone metabolism and growth in children

Growth retardation, decreased final height and renal osteodystrophy (ROD) are common complications of childhood chronic kidney disease (CKD), resulting from a combination of abnormalities in the growth hormone (GH) axis, vitamin D deficiency, hyperparathyroidism, hypogonadism, inadequate nutrition, cachexia and drug toxicity. The impact of CKD-associated bone and mineral disorders (CKD-MBD) may be immediate (serum phosphate/calcium disequilibrium) or delayed (poor growth, ROD, fractures, vascular calcifications, increased morbidity and mortality). In 2012, the clinical management of CKD-MBD in children needs to focus on three main objectives: (i) to provide an optimal growth in order to maximize the final height with an early management with recombinant GH therapy when required, (ii) to equilibrate calcium/phosphate metabolism so as to obtain acceptable bone quality and cardiovascular status and (iii) to correct all metabolic and clinical abnormalities that can worsen bone disease, growth and cardiovascular disease, i.e. metabolic acidosis, anaemia, malnutrition and 25(OH)vitamin D deficiency. The aim of this review is to provide an overview of the mineral, bone and vascular abnormalities associated with CKD in children in terms of pathophysiology, diagnosis and clinical management.

FGF-23 in children with CKD: a new player in the development of CKD-mineral and bone disorder

Disturbances in mineral and bone metabolism in children with chronic kidney disease (CKD) lead to specific abnormalities of skeletal homeostasis called CKD-mineral and bone disorder (CKD-MBD). These disturbances should be diagnosed and managed appropriately to prevent bone deformities and disturbed growth. Changes in the vitamin D and parathyroid hormone (PTH), and the subsequent alterations in calcium (Ca) and phosphate (P) homeostasis are considered responsible for the development of CKD-MBD. Recently, a phosphaturic hormone, the fibroblast growth factor-23 (FGF-23), has been reported as a key regulator of P and vitamin D metabolism. A number of recent studies in paediatric populations have documented that the FGF-23 levels are increased early in CKD, before any abnormalities in serum Ca, P or PTH are apparent. The elevated FGF-23 levels result in a negative P balance to maintain P homeostasis, inducing phosphaturia, independently of PTH, and suppressing vitamin D synthesis. Therefore, the bone-kidney-parathyroid endocrine axis mediated by FGF-23 should be a novel therapeutic target in clinical practice, even in early stages of CKD in children.

Growth hormone in chronic renal disease

Severe growth retardation (below the third percentile for height) is seen in up to one-third children with chronic kidney disease. It is thought to be multifactorial and despite optimal medical therapy most children are unable to reach their normal height. Under-nutrition, anemia, vitamin D deficiency with secondary hyperparathyroidism, metabolic acidosis, hyperphosphatemia, renal osteodystrophy; abnormalities in the growth hormone/insulin like growth factor system and sex steroids, all have been implicated in the pathogenesis of growth failure. Therapy includes optimization of nutritional and metabolic abnormalities. Failure to achieve adequate height despite 3-6 months of optimal medical measures mandates the use of recombinant GH (rGH) therapy, which has shown to result in catch-up growth, anywhere from 2 cm to 10 cm with satisfactory liner, somatic and psychological development.

Serum osteoprotegerin, RANKL and fibroblast growth factor-23 in children with chronic kidney disease

Osteoprotegerin (OPG), receptor activator of the nuclear factor κB ligand (RANKL) and fibroblast growth factor-23 (FGF-23) play a central role in renal osteodystrophy. We evaluated OPG/RANKL and FGF-23 levels in 51 children with chronic kidney disease (CKD) [n = 26 stage 3 or 4 (CKD3-4) and n = 25 stage 5 (CKD5)] and 61 controls. Any possible association with intact parathyroid hormone (iPTH) and bone turnover markers was also investigated. The OPG levels were lower in the CKD3-4 group (p < 0.001) and higher in the CKD5 group (p < 0.01) than in the controls, while RANKL levels did not differ. The FGF-23 levels were higher in both patient groups (p < 0.0001), while the levels of phosphate and iPTH were higher only in the CKD5 group (p < 0.0001). There were independent positive correlations between OPG and RANKL (β = 0.297, p < 0.01) and FGF-23 (β = 0.352, p < 0.05) and a negative correlation with the bone resorption marker TRAP5b (β = -0.519, p < 0.001). OPG was positively correlated with iPTH (R = 0.391, p < 0.01). An independent positive correlation between FGF-23 and phosphate (β = 0.368, p < 0.05) or iPTH (β = 0.812, p < 0.0001) was noted. In conclusion, we found that higher OPG levels in patients with CKD stage 5 correlated with the levels of RANKL, FGF-23, iPTH, and TRAP5b. These findings may reflect a compensatory mechanism to the negative balance of bone turnover. High FGF-23 levels in early CKD stages may indicate the need for intervention to manage serum phosphate (Pi) levels.

1,25(OH)2D3 alters growth plate maturation and bone architecture in young rats with normal renal function

Whereas detrimental effects of vitamin D deficiency are known over century, the effects of vitamin D receptor activation by 1,25(OH)₂D₃, the principal hormonal form of vitamin D, on the growing bone and its growth plate are less clear. Currently, 1,25(OH)₂D₃ is used in pediatric patients with chronic kidney disease and mineral and bone disorder (CKD-MBD) and is strongly associated with growth retardation. Here, we investigate the effect of 1,25(OH)₂D₃ treatment on bone development in normal young rats, unrelated to renal insufficiency. Young rats received daily i.p. injections of 1 µg/kg 1,25(OH)₂D₃ for one week, or intermittent 3 µg/kg 1,25(OH)₂D₃ for one month. Histological analysis revealed narrower tibial growth plates, predominantly in the hypertrophic zone of 1,25(OH)₂D₃-treated animals in both experimental protocols. This phenotype was supported by narrower distribution of aggrecan, collagens II and X mRNA, shown by in situ hybridization. Concomitant with altered chondrocyte maturation, 1,25(OH)₂D₃ increased chondrocyte proliferation and apoptosis in terminal hypertrophic cells. In vitro treatment of the chondrocytic cell line ATDC5 with 1,25(OH)₂D₃ lowered differentiation and increased proliferation dose and time-dependently. Micro-CT analysis of femurs from 1-week 1,25(OH)₂D₃-treated group revealed reduced cortical thickness, elevated cortical porosity, and higher trabecular number and thickness. 1-month administration resulted in a similar cortical phenotype but without effect on trabecular bone. Evaluation of fluorochrome binding with confocal microscopy revealed inhibiting effects of 1,25(OH)₂D₃ on intracortical bone formation. This study shows negative effects of 1,25(OH)₂D₃ on growth plate and bone which may contribute to the exacerbation of MBD in the CKD pediatric patients.

Bone mineral disorders in pediatric and adolescent renal transplant recipients

Incomplete resolution of abnormalities of mineral metabolism associated with CRF results in the relatively high prevalence of ROD in pediatric kidney recipients. This non-randomized, cross-sectional, and analytic-descriptive study on bone density, vitamin D, and mineral metabolism was performed in 57 children and adolescents who had received a total of 60 renal allografts in Shiraz, Iran. The height and weight of the patients were measured; their serum calcium (Ca), phosphorus (P), Alk-P, PTH, 25(OH)-vitamin D(3), BUN, creatinine, and electrolyte levels were analyzed, and a complete blood count was performed. In addition, standard radiologic bone assessments, which included conventional left hand-wrist radiography and bone mineral densitometry by the DXA technique, were carried out. Special pediatric software was used for age-related interpretation of the Z-scores of BMD. SPSS(®) software (version 15) was used for statistical analyses. We studied 57 patients (27 males [47.4%]) with a mean age of 18.7 ± 4.25 (9-27) yr and a mean age at transplantation of 13.1 ± 3.46 (4.5-20) yr. They had a post-transplantation follow-up of 67.1 ± 33.8 (6-132) months, and all had well-functioning allografts at enrollment. The mean height age of the patients was 11.9 ± 1.8 (6-15.5), and the mean bone age was 15.6 ± 3.3 (7-19) yr, which corresponded to mean height-age and bone-age retardations of 5.7 ± 2.3 (0.5-10.5) and 1.22 ± 1.47 (0-7) yr, respectively. Hyperphosphatemia and hypercalcemia were each found in nine patients (15.8%), hypophosphatemia in five (8.8%), and hypocalcemia in none of the patients. Seven out of 57 patients (12.3%) had a (Ca×P) product of more than 55 mg(2)/dL(2). Hyperparathyroidism was found in 27 (47.3%) and vitamin D(3) deficiency in four (7%) of the cases. The serum level of Alk-P was higher than the age-related normal range in 20 patients (35%). Left hand-wrist radiography showed no radiologic sign of ROD in any patient. The mean BMD Z-score was -1.77 ± 1.13 (-4.2-1.1) for the lumbar spine and -1.64 ± 0.89 (-3.9 to 1.9) for the femoral neck. "Stepwise backward regression" revealed a significant inverse correlation between the serum level of PTH and the GFR of the transplanted kidney; this correlation was independent from the influence of other variables such as Ca, P, and Alk-P (p = 0.011, β = -1.556). Bone age and height age both showed significant correlations with age at transplantation and serum levels of P (p < 0.001), but only bone age had a meaningful correlation with Alk-P (p = 0.036). The BMD Z-scores showed statistically meaningful correlations with the serum level of Alk-P, which were independent from the influence of other variables such as Ca, P, and PTH (p ≤ 0.002). Our study revealed a relatively high prevalence of bone mineral disorder in pediatric kidney recipients, which suggests the need for a routine program for periodic screening of these patients to facilitate early diagnosis of either persistent or evolving manifestations of disturbed mineral metabolism, especially ROD.

Ten-year experience with sevelamer and calcium salts as phosphate binders

Most patients with chronic kidney disease experience abnormalities in serum calcium, phosphorus, parathyroid hormone, and vitamin D metabolism. These can lead to vascular calcification (VC), which has been associated with increased risk for cardiovascular disease and mortality. Although hyperphosphatemia is believed to be a risk factor for mortality and VC, no randomized trial was ever designed to demonstrate that lowering phosphate reduces mortality. Nonetheless, binders have been used extensively, and the preponderance of evidence shows that sevelamer slows the development of VC whereas calcium salts do not. Four studies have demonstrated a slower progression of VC with sevelamer than with calcium-containing binders, although a fifth study showed nonsuperiority. Conversely, the results on mortality with sevelamer have been variable, and data on calcium-based binders are nonexistent. Improved survival with sevelamer was demonstrated in a small randomized clinical trial, whereas a larger randomized trial failed to show a benefit. In addition, preclinical models of renal failure and preliminary clinical data on hemodialysis patients suggest a potential benefit for bone with sevelamer. Meanwhile, several randomized and observational studies suggested no improvement in bone density and fracture rate, and a few noted an increase in total and cardiovascular mortality in the general population given calcium supplements. Although additional studies are needed, there are at least indications that sevelamer may improve vascular and bone health and, perhaps, mortality in hemodialysis patients, whereas data on calcium-based binders are lacking.

Self-adjustment of phosphate binder dose to meal phosphorus content improves management of hyperphosphataemia in children with chronic kidney disease

BACKGROUND

Hyperphosphataemia in patients with chronic kidney disease (CKD) is associated with mineral and bone disorder and increased cardiovascular mortality. Despite phosphate binders (PB), nutrition counselling and dialysis therapy, the prevalence of hyperphosphataemia remains unacceptably high. It was hypothesized that an inadequate relation of PB dose to meal inorganic phosphorus (iP) content may be an important factor for failure of phosphate management.

METHODS

The innovative 'Phosphate Education Program' (PEP) bases on patient empowerment to eye-estimate meal iP content by newly defined 'Phosphate Units' (PU; 1 PU per 100 mg phosphorus) and self-adjust PB dosage to dietary iP intake by an individually prescribed PB/PU ratio (PB pills per PU). In a prospective study, 16 children (aged 4-17 years) with CKD and their parents were trained with the PEP concept and followed up for 24 weeks for changes in serum electrolyte levels, dietary behaviour and PB dose.

RESULTS

Within 6 weeks after PEP training, the percentage of children with serum phosphate (PO) >1.78 mmol/l dropped from 63% (10/16) to 31% (5/16). Mean serum PO level decreased from 1.94 ± 0.23 at baseline to 1.68 ± 0.30 (SD) mmol/l in Week 7-12 (P = 0.02) and to 1.78 ± 0.36 (SD) mmol/l in Week 19-24 (P = 0.2), whereas serum calcium [2.66 ± 0.3 vs 2.60 ± 0.23 (SD) mmol/l in Weeks 7-12 (P = 0.45) and 2.66 ± 0.23 (SD) mmol/l in Week 19-24 (P = 0.21)] and serum potassium [4.69 ± 0.48 vs 4.58 ± 0.68 (SD) mmol/l in Week 7-12 (P = 0.40) and 4.65 ± 0.49 (SD) mmol/l in Week 19-24 (P = 0.73)] remained unchanged. The mean daily PB dose rose from 6.3 ± 2.9 to 8.2 ± 5.4 (SD) pills during observation period with an increased meal-to-meal variability (P = 0.04). Dietary iP intake was not affected by PEP concept.

CONCLUSION

The empowerment of children with CKD and their parents to self-adjust PB dose to eye-estimated meal iP content significantly improved management of hyperphosphataemia without reducing dietary iP intake.

Vitamin D deficiency in children with chronic kidney disease: uncovering an epidemic

BACKGROUND

Vitamin D deficiency in children adversely affects bone development by reducing mineralization. Children with chronic kidney disease are at risk for altered bone development from renal osteodystrophy and concomitant vitamin D deficiency. The pediatric Kidney Disease Outcomes Quality Initiative guidelines suggest measuring serum 25-hydroxyvitamin D (25[OH]D) levels if serum parathyroid hormone levels are above the target range for chronic kidney disease stages 2 and beyond, but the magnitude of vitamin D deficiency in children with chronic kidney disease is not well studied.

OBJECTIVES

The purpose of this work was to determine whether children with chronic kidney disease had vitamin D deficiency, to evaluate whether the prevalence of vitamin D deficiency changed over time, and to examine seasonal and ethnic differences in 25(OH)D levels.

METHODS

25(OH)D levels in children with chronic kidney disease (stages 1-5) were measured over a 10-year period from 1987 to 1996. Data were also collected for a contemporary group of patients from 2005 to 2006. RESULTS. The prevalence of vitamin D deficiency ranged from 20% to 75% in the decade studied. There was a significant trend for decreasing 25(OH)D levels over the decade, both at the group and individual levels. Seasonal variation was noted. In our contemporary population with chronic kidney disease, the mean 25(OH)D level was 21.8 ng/mL; we found a prevalence of vitamin D deficiency of 39%. Black and Hispanic patients had lower levels of 25(OH)D than white patients.

CONCLUSIONS

Children with chronic kidney disease have great risk for vitamin D deficiency, and its prevalence was increasing yearly in the studied decade. Contemporary data show that vitamin D deficiency remains a problem in these children. Sunlight exposure and ethnicity play a role in levels of 25(OH)D. Our data support the recent pediatric Kidney Disease Outcomes Quality Initiative guidelines for measurement of 25(OH)D levels in children with chronic kidney disease and secondary hyperparathyroidism.