Severe bone disease and low bone mineral density after juvenile renal failure

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.

Disparities in dialysis treatment and outcomes for Dutch and Belgian children with immigrant parents

BACKGROUND

In Belgium and the Netherlands, up to 40% of the children on dialysis are children with immigrant parents of non-Western European origin (non-Western). Concerns exist regarding whether these non-Western patients receive the same quality of care as children with parents of Western European origin (Western). We compared initial dialysis, post-initial treatment, and outcomes between non-Western and Western patients on dialysis.

METHODS

All children <19 years old on chronic dialysis in the Netherlands and Belgium between September 2007 and May 2011 were included in the study. Non-Western patients were defined as children of whom one or both parents were born in non-Western countries.

RESULTS

Seventy-nine of the 179 included patients (44%) were non-Western children. Compared to Western patients, non-Western patients more often were treated with hemodialysis (HD) instead of peritoneal dialysis (PD) as first dialysis mode (52 vs. 37%, p = 0.046). Before renal transplantation, non-Western patients were on dialysis for a median (range) of 30 (5-99) months, vs. 15 (0-66) months in Western patients (p = 0.007). Renal osteodystrophy was diagnosed in 34% of non-Western vs. 18% of Western patients (p = 0.028). The incidence rate ratio [95% confidence interval] for acute peritonitis was 2.44 [1.43-4.17] (p = 0.032) for non-Western compared to Western patients.

CONCLUSIONS

There are important disparities between children on chronic dialysis with parents from Western European origin and those from non-Western European origin in the choice of modality, duration, and outcomes of dialysis therapy.

Bone assessment in children with chronic kidney disease: data from two new bone imaging techniques in a single-center pilot study

Bone damage in children with chronic kidney disease (CKD) is a challenge for pediatric nephrologists. Areal measurements of bone mineral density (BMD) by dual x-ray absorptiometry (DXA) have been routinely performed to assess bone mass but recent international guidelines have concluded that DXA was of less value in CKD. The aim of this study is to evaluate bone quality in CKD children using new bone imaging techniques in a pilot cross-sectional single-center study. We performed bone imaging (high-resolution peripheral quantitative computed tomography, HR-pQCT, XtremeCT, Scanco Medical AG, Switzerland), to assess compartmental volumetric BMD and trabecular microarchitecture in 22 CKD children and 19 controls. In seven younger patients (i.e., under 10 years of age), we performed bone texture analysis (BMA, D3A Medical Systems, France) in comparison to 15 healthy prepubertal controls. Among older children, CKD patients had significantly lower height and body weight without significant impairment of BMD and microarchitecture than healthy controls. In univariate analysis, there were significant correlations between cortical BMD and glomerular filtration rate (r= -0.46), age (r=0.60) and body mass index (r=0.67). In younger children, bone texture parameters were not different between patients and controls. Our results did not show significant differences between healthy controls and CKD children for compartmental bone densities and microarchitecture, but the small sample size and the heterogeneity of the CKD group require caution in the interpretation. Novel bone imaging techniques seem feasible in children, and further longitudinal studies are required to thoroughly explore long-term cardiovascular and bone consequences of phosphate-calcium metabolism deregulation during CKD.

Value of the new bone classification system in pediatric renal osteodystrophy

BACKGROUND AND OBJECTIVES

Although lesions of renal osteodystrophy have traditionally been defined by bone turnover, alterations in skeletal mineralization and volume are also prevalent and may contribute to significant morbidity in patients with chronic kidney disease (CKD). The study presented here was undertaken to compare the traditional spectrum of renal osteodystrophy defined by bone turnover to a new classification system that includes T (turnover), M (mineralization), and V (volume) and to determine the value of biochemical parameters as predictors of specific TMV lesions.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Pediatric patients (n = 161) treated with peritoneal dialysis were enrolled into the study.

RESULTS

Increased bone turnover and abnormal mineralization were prevalent (57% and 48%, respectively); bone volume was normal or increased in all subjects. Predictive algorithms for different skeletal diagnoses were established by Classification and regression tree analysis. Serum parathyroid hormone (PTH) less than 400 pg/ml in combination with alkaline phosphatase values less than 400 IU/L provided the highest correct prediction rate for patients with both normal bone turnover and normal mineralization. Levels of PTH were higher and serum calcium levels were lower in patients with defective mineralization, irrespective of bone turnover.

CONCLUSIONS

Although no single biochemical marker is able to provide a complete assessment of renal osteodystrophy, a combination of serum calcium, alkaline phosphatase, and PTH levels may lead to a more precise noninvasive assessment of turnover and mineralization abnormalities in this population.

Children with chronic kidney disease: a 3-year prospective study of growth, bone mass and bone turnover

AIM

Children with chronic kidney disease (CKD) are at risk of developing skeletal problems. This 3-year prospective study investigated the development of bone mass and bone turnover in children with CKD.

METHODS

Fifteen patients, 4-15 years, were included with a median glomerular filtration rate of 48 (range 8-94) mL/min/1.73 m(2). Bone mineral density (BMD) and markers of bone and mineral metabolism were investigated over a 3-year period.

RESULTS

Growth was satisfactory but a delayed bone age was observed. Total body bone mineral density (TBBMD) Z-scores were below zero in five patients at start and after 3 years, but none had a Z-score below -2.5. Lumbar spine BMD Z-scores were below zero in three patients at start and in five patients after 3 years. The median TBBMD and lumbar spine Z-scores did not change during the study period. Eleven CKD patients had increased PTH levels at baseline and 13 patients after 3 years. Most children had normal levels of leptin and vitamin D. Almost 50% of the patients had increased osteoprotegerin levels after 3 years.

CONCLUSION

A normal BMD does not exclude mineral bone disorder in patients with CKD, yet the BMD Z-scores were well preserved and most markers of bone turnover were within the reference intervals.

Relationship between plasma fibroblast growth factor-23 concentration and bone mineralization in children with renal failure on peritoneal dialysis

CONTEXT

Fibroblast growth factor (FGF)-23 is produced in bone, and circulating levels are markedly elevated in patients with end-stage kidney disease, but the relationship between plasma levels of FGF-23 and bone histology in dialysis patients with secondary hyperparathyroidism is unknown.

OBJECTIVE

The aim of the study was to evaluate the correlation between plasma levels of FGF-23 and bone histology in pediatric patients with end-stage kidney disease who display biochemical evidence of secondary hyperparathyroidism.

DESIGN

We performed a cross-sectional analysis of the relationship between plasma FGF-23 levels and bone histomorphometry.

SETTING

The study was conducted in a referral center.

STUDY PARTICIPANTS

Participants consisted of forty-nine pediatric patients who were treated with maintenance peritoneal dialysis and who had serum PTH levels (1st generation Nichols assay) greater than 400 pg/ml.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURE

Plasma FGF-23 levels and bone histomorphometry were measured.

RESULTS

No correlation existed between values of PTH and FGF-23. Bone formation rates correlated with PTH (r = 0.44; P < 0.01), but not with FGF-23. Higher FGF-23 concentrations were associated with decreased osteoid thickness (r = -0.49; P < 0.01) and shorter osteoid maturation time (r = -0.48; P < 0.01).

CONCLUSIONS

High levels of FGF-23 are associated with improved indices of skeletal mineralization in dialyzed pediatric patients with high turnover renal osteodystrophy. Together with other biomarkers, FGF-23 measurements may indicate skeletal mineralization status in this patient population.

Cinacalcet does not affect longitudinal growth but increases body weight gain in experimental uraemia

BACKGROUND

Cinacalcet (CIN) efficiently suppresses parathyroid hormone (PTH) secretion by the activation of the calcium-sensing receptor (CaR). Epiphyseal chondrocytes also express the CaR and its activation promotes cell proliferation and differentiation in vitro. Hence, the impact of CIN on the growth plate function requires assessment before routine administration in children.

METHODS

We treated subtotally nephrectomized (SNX) and sham-operated, ad lib and pair-fed Sprague-Dawley rats with CIN (15 mg/kg day) or solvent (S) for 14 days p.o. and assessed whole body and tibia length gain, growth plate morphology, osseous front advance (OFA) (calcein staining) and chondrocyte proliferation rate [5-bromo-2'-deoxyuridine (BrdU) staining].

RESULTS

Total body length gain did not differ after 7 and 14 days (SNX + CIN 2.9 +/- 0.6, SNX + S 3.0 +/- 0.7; sham + CIN 4.2 +/- 0.4, sham + S 4.5 +/- 0.4; sham pair-fed + CIN 3.3 +/- 0.5, sham pair-fed + S 3.5 +/- 0.6 cm/14 days; P = n.s.). Tibia length, the height of the total growth plate and the hypertrophic zone, OFA and chondrocyte proliferation rate were similar with CIN and S. Serum Ca(2+) declined with CIN treatment; PTH was 61% lower in CIN- compared to S-treated SNX (P < 0.05). Food intake was similar, whereas body weight gain (21.6 +/- 8.7 versus 12.7 +/- 11.2 g) and body weight gain per food intake (141 +/- 50 versus 77 +/- 70 g/kg) improved in CIN- versus S-treated SNX animals (P < 0.05).

CONCLUSION

CIN treatment does not impact on growth plate chondrocyte function in uraemic rats, but improves food efficiency and body weight gain.

A national conference to determine research priorities in pediatric solid organ transplantation

The need for evidence-based practice guidelines requires high quality, carefully controlled clinical research trials. This multidisciplinary conference attempted to: identify urgent clinical and research issues, identify obstacles to performing clinical trials, develop concepts for organ-specific and all-organ research and generate a report that would serve as a blueprint for future research initiatives. A few themes became evident. First, young children present a unique immunologic environment which may lead to tolerance, therefore, including young children in immunosuppression withdrawal and tolerance trials may increase the potential benefits of these studies. Second, adolescence poses significant barriers to successful transplantation. Non-adherence may be insufficient to explain poorer outcomes. More studies focused on identification and prevention of non-adherence, and the potential effects of puberty are required. Third, the relatively naive immune system of the child presents a unique opportunity to study primary infections and alloimmune responses. Finally, relatively small numbers of transplants performed in pediatric centers mandate multicenter collaboration. Investment in registries, tissue and DNA repositories will enhance productivity. The past decade has proven that outcomes after pediatric transplantation can be comparable to adults. The pediatric community now has the opportunity to design and complete studies that enhance outcomes for all transplant recipients.

Chronic kidney disease mineral and bone disorder in children

Childhood and adolescence are crucial times for the development of a healthy skeletal and cardiovascular system. Disordered mineral and bone metabolism accompany chronic kidney disease (CKD) and present significant obstacles to optimal bone strength, final adult height, and cardiovascular health. Decreased activity of renal 1 alpha hydroxylase results in decreased intestinal calcium absorption, increased serum parathyroid hormone levels, and high-turnover renal osteodystrophy, with subsequent growth failure. Simultaneously, phosphorus retention exacerbates secondary hyperparathyroidism, and elevated levels contribute to cardiovascular disease. Treatment of hyperphosphatemia and secondary hyperparathyroidism improves growth and high-turnover bone disease. However, target ranges for serum calcium, phosphorus, and parathyroid hormone (PTH) levels vary according to stage of CKD. Since over-treatment may result in adynamic bone disease, growth failure, hypercalcemia, and progression of cardiovascular calcifications, therapy must be carefully adjusted to maintain optimal serum biochemical parameters according to stage of CKD. Newer therapeutic agents, including calcium-free phosphate binding agents and new vitamin D analogues, effectively suppress serum PTH levels while limiting intestinal calcium absorption and may provide future therapeutic alternatives for children with CKD.

Bone mass, biochemical markers and growth in children with chronic kidney disease: a 1-year prospective study

AIM

This study was designed to investigate bone mineral density (BMD), growth parameters and biochemical markers in children with chronic kidney disease (CKD).

METHODS

Sixteen patients, 4-18 years, with CKD were prospectively followed for 1 year. Auxological data, body composition, BMD by dual-energy X-ray absorptiometry, bone age, bone turnover markers, vitamin D, parathyroid hormone (PTH), leptin, osteoprotegerin, insulin-like growth factor-I (IGF-I) and IGF binding protein-3 were measured. A questionnaire regarding bone health and diet was also performed.

RESULTS

Delayed bone age was observed (n = 11) and the BMD Z-scores for total body were below zero in seven patients. However, total body BMD (TBBMD) increased in 12 patients. Most patients had increased osteocalcin and carboxy-terminal telopeptide of type I collagen, but normal alkaline phosphatase, type I procollagen intact amino-terminal propeptide and tartrate-resistant acid phosphatase 5b. Ten patients had increased PTH. Most children had normal levels of leptin, osteoprotegerin, IGF-I and IGFBP-3. Leptin, at baseline, correlated with differences in TBBMD over 1 year.

CONCLUSIONS

Only seven (44%) had negative Z-scores and TBBMD increased over 1 year. Bone markers at baseline did not predict the longitudinal changes in BMD.

Bone mineral density in children with chronic renal failure

Bone mineral density (BMD) is important in children and adolescents because of its relationship to long-term skeletal health, and because, in adults with chronic renal failure (CRF), a relationship between low BMD and vascular calcification has been suggested. To investigate the relationship between BMD and manipulable factors that might affect it, i.e. plasma calcium, phosphate and parathyroid hormone (PTH), 64 patients with a median glomerular filtration rate (GFR) of 31 (range 7-60) ml min(-1) 1.73 m(-2) and median age of 10.0 (4.1-16.9) years were followed over 1.3 (0.7-1.7) years at an average of 5 (3-14) clinic visits. At one visit, BMD of the lumbar spine was measured by dual energy X-ray absorptiometry. The mean BMD Z-score was normal (=0.0). Overall mean calcium, phosphate and PTH levels were in their respective normal ranges. The majority of the patients (72%) were treated with calcium carbonate, mean dose 65 mg kg(-1) day(-1); prescription was positively related to serum calcium levels and calcium-phosphate product (P=0.012 and P<0.01 respectively). Almost all patients (98%) were treated with alfacalcidol, mean dose 12 ng kg(-1) day(-1); prescription was not related to investigated factors. Patients grew well; there was no change in height standard deviation score (DeltaHtSDS=0.0). Normal BMD Z-score for age and sex can be achieved in children with CRF managed with the aim of maintaining normal PTH levels by dietary phosphate restriction, calcium-based phosphate binders and small doses of alfacalcidol. Further investigation of the underlying bone by the use of biopsy and histomorphometry is required to determine actual bone health.

Quantitative ultrasound in monitoring of skeletal status in adults with end-stage renal disease

The aim of the longitudinal study was to assess skeletal status in 29 subjects (18 males and 11 females) with end-stage renal disease (ESRD) being on regular hemodialysis. Control group consisted of 494 healthy subjects (305 males and 189 females). Skeletal status was evaluated by quantitative ultrasound measurements at the hand phalanges using DBM Sonic 1200 (IGEA, Carpi, Italy), which measures amplitude-dependent speed of sound (Ad-SoS, in m/s), performed three times: at the baseline, six and 12 months later. A precision expressed in root mean square-CV% was 0.72% in males and 0.43% in females. The values of Ad-SoS, T-score and Z-score at the baseline were significantly lower than in controls (p < 0.05). The mean values of Ad-SoS decreased over a period of observation; in the whole group from 1979 +/- 106 m/s to 1928 +/- 105 m/s, p < 0.0001, in males from 2003 +/- 93 m/s to 1949 +/- 111 m/s, p < 0.001 and in females from 1940 +/- 121 m/s to 1894 +/- 108 m/s, p < 0.05. Ad-SoS Z-scores dropped significantly over a period of the study in whole group (-1.14 +/- 1.64 to -2.08 +/- 2.26, p < 0.01), in males (-0.63 +/- 1.44 to -1.74 +/- 2.29, p < 0.0001) and in females nonsignificant decrease was observed. Using the least significant change (LSC) values for skeletal measurement, a decrease in Ad-SoS was noted in 15 subjects (52%). The values of PTH were over a normal limit. In the whole group main factors negatively influencing current Ad-SoS values were duration of dialysis, age and PTH. The skeletal status in subjects with ESRD on hemodialysis was seriously affected, and longitudinal measurements showed its aggravation over a time of the study.

Chronic acidosis-induced growth retardation is mediated by proton-induced expression of Gs protein

The etiology of skeletal growth retardation accompanying metabolic acidosis is not clear. Using ex vivo models for endochondral ossification, we showed that the cAMP/PKA pathway, probably triggered by proton sensitive G-protein-coupled receptors, is responsible for impaired skeletal growth in acidosis.

INTRODUCTION

Chronic metabolic acidosis (CMA) is very often accompanied by skeletal growth retardation. We have previously shown in an ex vivo model of endochondral ossification that murine mandibular condyles subjected to acidic conditions exhibit growth retardation accompanied by a decline of insulin-like growth factor-I (IGF-I) and its receptors. PTH-induced ameliorative effects on the CMA-induced growth retardation of the mandibular condyle are partially mediated by protein kinase C (PKC). In this study we explored the mechanisms underlying the acidosis-induced growth retardation; in particular, the involvement of the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) cellular pathway in the process.

MATERIALS AND METHODS

Mandibular condyles from neonatal mice or mandibular condyle derived chondrocytes (MCDCs) were incubated for 3 days under either control or acidic conditions or in the presence of cAMP-regulating factors (cAMPrf) such as forskolin, iso-butyl methyl xanthine (IBMX), or 8-Br cAMP. The effects on proliferation and differentiation of the cultures as well as on phosphorylation of cAMP responsive element binding protein (CREB) and increased expression of the alpha subunit, Gs were determined. The intracellular pH was detected using the acridine orange assay.

RESULTS

Our results show that, under acidic conditions, PKA levels were increased. H89 abolished the adverse effects of acidosis on condylar development and restored IGF-I and IGF-I receptors (IGF-IR) levels. The inhibitory effects of acidosis on proliferation and differentiation of cartilaginous cells were mimicked by cAMPrf. We have also shown that acidosis stimulates activation of Gs trimeric protein and CREB phosphorylation. GDPbetaS--a Gs antagonist--abolished the acidosis-induced condylar growth arrest. Using an acridine orange assay, we showed that the intracellular environment is not acidified under acidic conditions.

CONCLUSIONS

Our results indicate that the adverse effects of acidosis on skeletal growth centers are mediated at least in part by the cAMP/PKA cellular pathway. We speculate that high proton concentrations exerted by acidosis conditions stimulate proton sensitive G-protein-coupled receptors, which are mediated by the cellular cAMP/PKA pathway and induce skeletal growth retardation.

Watching bone cells at work: what we can see from bone biopsies

Histomorphometric analysis of iliac bone samples is a key tool for studying bone metabolism and, to a lesser extent, bone mass and structure. Two types of bone metabolic activity can be distinguished: modeling and remodeling. Both processes are performed by the same effector cells, osteoblasts and osteoclasts, but differ in the way these cells are arranged. The main effect of remodeling is to renew bone, whereas modeling can lead to rapid changes in bone shape, size and mass. Standard histomorphometric analysis focuses on trabecular bone and therefore mainly provides information on remodeling. Remodeling activity changes markedly with age during development. This must be taken into account when histomorphometry is used in the pediatric setting. Remodeling disorders encountered in the context of pediatric renal bone disease include mineralization defects, as well as abnormally high remodeling activity due to secondary hyperparathyroidism or suppressed remodeling activity as a consequence of over-treatment. Children and adolescents with severe bone fragility should have a bone biopsy unless the diagnosis is obvious from noninvasive examinations. Histomorphometric analysis of transiliac bone biopsy samples is especially valuable in clinical studies, as this method provides safety and efficacy data that cannot be obtained in any other way.

Long-term outcomes of children with end-stage renal disease

Long-term survival of children with end-stage renal disease (ESRD) has increased in the last 20 years, but the mortality rate remains high. Cardiovascular disease accounts for 40 to 50% of all deaths, infectious disease for about 20%. A prolonged period of dialysis versus having a renal graft and persistent hypertension are mortality risk factors. The prevalence of the various morbidities is high among those who have reached adulthood. Nearly 50% of all these patients suffer from left ventricular hypertrophy and life-threatening vascular changes; nearly one third has clinical signs of metabolic bone disease. This accounts for both dialysis and transplant recipients. The chance of getting cancer is increased ten times compared to the general population; skin cancer and non-Hodgkin lymphomas are most commonly reported. A long period of dialysis at childhood is associated with impairment of both cognitive and educational attainment. However, despite all these negative outcomes, the health perception of young adults with childhood onset ESRD is positive. Research and therapy in children with ESRD should focus not only on prevention of graft failure, but also on prevention of co-morbidity, especially cardiovascular disease, life-threatening infections and malignancies. Early transplantation, more extended forms of frequent hemodialysis in those who can not be transplanted, a more rigorous treatment of hypertension, avoidance or at least dosage reduction of calcium-containing phosphate binders, reduction of the chronic inflammatory state, and tailor made anti-rejection therapy after transplantation may all be targets to improve the outcome in future patients.

Skeletal status in adolescents with end-stage renal failure: a longitudinal study

In a longitudinal study, bone status was assessed in adolescents and young adults aged 15.3+/-3.4 years at the onset of the study with end-stage renal failure (ESRF). The group consisted of 18 subjects (11 females and seven males), of whom nine patients were on hemodialysis and nine patients on peritoneal dialysis. Six patients were previous or current glucocorticoid (GCS) users. Renal failure was recognized before 6.1+/-4.1 years, and dialysis was performed for 3.0+/-2.0 years. Follow-up took placed 8.6+/-0.8 and 21.7+/-2.5 months later, and the following data were collected: bone mineral density (BMD) at the spine (s-BMD) and total body (TB-BMD) using DPX-L (Lunar, USA); quantitative ultrasound by DBM 1200 (IGEA, Italy) at the hand phalanges (Amplitude-dependent Speed of Sound, Ad-SoS), serum concentration of i-PTH, total calcium, ionized calcium and phosphate. Tanner stages were also evaluated. The mean values of BMD measurements and Ad-SoS were stable during a period of observation, and a mean Z-score for TB-BMD was significantly lower at the third versus baseline value (-1.87+/-1.75 versus -1.49+/-1.53, P<0.05). Z-scores for s-BMD and Ad-SoS decreased non-significantly. Changes in s-BMD and TB-BMD Z-scores were influenced by changes in body size and changes in biochemical parameters, and a change in Ad-SoS Z-score was not dependent on these factors. The values of second (P<0.05) and third (P<0.01) s-BMD Z-score were significantly lower in GCS treated subjects, and longitudinal change in spine Z-score was greater in GCS treated patients versus others (P<0.05). Duration of ESRF, duration and type of dialysis and gender did not influence skeletal variables. Skeletal measurements correlated significantly with Tanner stages (besides the correlation with Ad-SoS in the first measurement, r ranged from 0.5 to 0.72, P<0.05), and changes in Tanner stages observed over a period of observation did not correlate with changes in skeletal variables. Among laboratory variables, the following non-significant tendencies to change were observed: serum concentration of i-PTH and phosphate increased, and total and ionized calcium decreased. In conclusion, adolescent subjects with ESRF treated with dialysis showed stable mean values of skeletal measurements, and these were expressed as Z-scores, a tendency to drop was observed. The lack of an increase observed in normal healthy subjects of the same age, and low values in Z-scores, indicates that skeletal status is seriously affected in subjects with ESRF.

Bone mineral density and bone turnover markers in children with chronic renal failure

Bone mineral density (BMD) at lumbar spine (L2-L4) was measured by dual-energy X-ray absorptiometry (DEXA) in 21 children with predialysis chronic renal failure (CRF) and 44 children with end-stage renal failure (ESRF) on regular hemodialysis. BMD results were expressed as Z-scores. Osteopenia was documented in 13 predialysis patients (61.9%) and 26 patients (59.1%) with ESRF. No significant correlation was observed between Z-scores and the duration of CRF or estimated creatinine clearance. In osteopenic children there was a negative correlation between Z-scores and serum phosphorus (r=-0.61, P=0.004), intact parathyroid hormone (iPTH) (r=-0.47, P=0.03), and bone-specific alkaline phosphatase (r=-0.52, P=0.02) and a positive correlation with total calcium (r=0.41, P=0.07) and 25-hydroxycholecalciferol (r=0.53, P=0.02). Osteopenic children who had iPTH values > or = 200 pg/ml were more osteopenic than those who had lower iPTH levels (P=0.006). In conclusion, osteopenia, assessed by DEXA, is frequent in children with CRF. It occurs early irrespective of the duration or the severity of CRF. In children with ESRF the degree of osteopenia is correlated with laboratory markers of renal osteodystrophy and patients with biochemical findings of secondary hyperparathyroidism are more osteopenic than the others.

Osseous complications of pediatric transplantation

Adult stature and peak bone mass are achieved through childhood growth and development. Multiple factors impair this process in children undergoing solid organ transplantation, including chronic illness, pretransplant osteodystrophy, use of medications with negative impact on bone, and post-transplant renal dysfunction. While growth delay and short stature remain common, the most severe forms of transplant-related bone disease, fracture and avascular necrosis, appear to have become less common in the pediatric age group. Osteopenia is very prevalent in adult transplant recipients and probably also in pediatrics, but its occurrence and sequelae are difficult to study in these groups due to methodological shortfalls of planar densitometry related to short stature and altered patterns of growth and development. Although the effect on lifetime peak bone mass is not clear, data from adult populations suggest an elevated long-term risk of bone disease in children receiving transplants. Optimal management of pretransplantation osteodystrophy, attention to post-transplant renal insufficiency among both renal and non-renal transplant patients, reduction of steroid dose in select patients, and supplementation with calcium plus vitamin D during expected periods of maximal bone loss may improve bone health. Careful research is required to determine the role of bisphosphonate therapy in pediatric transplantation.