Nutrition in children with kidney disease: pitfalls of popular assessment methods

Children with chronic kidney disease (CKD) are considered at high risk for protein-energy malnutrition. Clinical practice guidelines generally recommend an evaluation of numerous nutritional parameters to give a complete and accurate picture of nutritional status. This review summarizes the potential limitations of commonly used methods of nutritional assessmentin the setting of CKD. Unrecognized fluid overload and inappropriate normalization of body composition measures are the most important factors leading to misinterpretation of the nutritional assessment in CKD. The importance of expressing body composition measures relative to height or height-age in a population in whom short stature and pubertal delay are highly prevalent is emphasized. The limitations of growth as a marker for nutritional status are also addressed. In addition, the prevailing belief that children with CKD are at high risk for malnutrition is challenged.

Deficits in size-adjusted bone mass in children with Alagille syndrome

OBJECTIVES

To describe bone status in children with Alagille syndrome (AGS) and healthy control children adjusted for age, gender and height (HT), and to identify dietary intake and AGS-related factors associated with bone status.

METHODS

Prepubertal children with AGS and healthy controls comparable in age and ethnicity were evaluated. Subjects were > or =4 years of age, prepubertal and had whole body (WB) and/or lumbar spine (LS) dual energy X-ray absorptiometry (DXA) scans of acceptable quality. Anthropometric (weight, HT), diet and AGS-specific data (e.g., coefficient of fat absorption, labs, liver transplantation) were also collected. Bone area (BA), bone mineral content (BMC) and HT were log transformed for best fit. Bone data were analyzed unadjusted, adjusted for gender, age and HT, and as HT-specific z-scores.

RESULTS

AGS and control groups were similar in age, pubertal status and ethnicity. Children with AGS were small-for-age, had decreased BA and BMC-for-age, and decreased WB BA and BMC-for-HT z-scores compared to healthy controls. Prevalence of low BMC-for-HT z-scores (< -2) among AGS subjects was 20% for the WB and 39% for the LS. Bone mineralization was positively related to fat absorption but not dietary intake.

CONCLUSIONS

Children with AGS have deficits in bone size and bone mass relative to body size. Modifiable factors, such as treatment of malabsorption should be explored as an early focus of AGS care to prevent bone fragility.

Vitamin D insufficiency in steroid-sensitive nephrotic syndrome in remission

Serum 25-hydroxyvitamin D [25(OH)D] concentrations are the best indicator of vitamin D nutritional status. We measured serum 25(OH)D concentrations in 94 healthy controls and in 41 subjects (aged 4-22 years) with steroid-sensitive nephrotic syndrome (SSNS) in remission. Children with remitted SSNS had significantly lower 25(OH)D concentrations than healthy controls (median 16.4 ng/ml versus 23.9 ng/ml, P<0.001). In a multivariable logistic regression model, the odds ratios (OR) of vitamin D insufficiency [25(OH)D <20 ng/ml] were independently increased in SSNS subjects [OR 11.2 (95% confidence interval 3.5-36.2)], non-whites [OR 12.9 (4.6-36.2)], older children [OR 1.20 per year (1.06-1.36)], and winter months [OR 6.7 (2.5-18.4)]. Within the SSNS subjects, multiple linear regression determined that serum 25(OH)D concentrations were not associated with SSNS disease characteristics measured in this study, such as duration of disease, number of relapses, cumulative glucocorticoids, and interval since last relapse. In conclusion, children with remitted SSNS have lower serum 25(OH)D concentrations than healthy controls. This difference persisted after adjusting for the potential confounding effects of age, race, season, and milk intake. Children with remitted SSNS may benefit from routine measurement of 25(OH)D, but the clinical significance of low 25(OH)D in this population remains unclear.

Whole body BMC in pediatric Crohn disease: independent effects of altered growth, maturation, and body composition

Whole body BMC was assessed in 104 children and young adults with CD and 233 healthy controls. CD was associated with significant deficits in BMC and lean mass, relative to height. Adjustment for lean mass eliminated the bone deficit in CD. Steroid exposure was associated with short stature but not bone deficits relative to height.

INTRODUCTION

Children with Crohn disease (CD) have multiple risk factors for impaired bone accrual. The confounding effects of poor growth and delayed maturation limit the interpretation of prior studies of bone health in CD. The objective of this study was to assess BMC relative to growth, body composition, and maturation in CD compared with controls.

MATERIALS AND METHODS

Whole body BMC and lean mass were assessed by DXA in 104 CD subjects and 233 healthy controls, 4-26 years of age. Multivariable linear regression models were developed to sequentially adjust for differences in skeletal size, pubertal maturation, and muscle mass. BMC-for-height z scores were derived to determine CD-specific covariates associated with bone deficits.

RESULTS

Subjects with CD had significantly lower height z score, body mass index z score, and lean mass relative to height compared with controls (all p < 0.0001). After adjustment for group differences in age, height, and race, the ratio of BMC in CD relative to controls was significantly reduced in males (0.86; 95% CI, 0.83, 0.94) and females (0.91; 95% CI, 0.85, 0.98) with CD. Adjustment for pubertal maturation did not alter the estimate; however, addition of lean mass to the model eliminated the bone deficit. Steroid exposure was associated with short stature but not bone deficits.

CONCLUSION

This study shows the importance of considering differences in body size and composition when interpreting DXA data in children with chronic inflammatory conditions and shows an association between deficits in muscle mass and bone in pediatric CD.

Interactions between growth and body composition in children treated with high-dose chronic glucocorticoids

BACKGROUND

Glucocorticoid therapy retards growth during childhood and is believed to lead to a Cushingoid body habitus. However, despite prolonged, repeated courses of glucocorticoid, children with steroid-sensitive nephrotic syndrome (SSNS) have almost normal adult height. Little information exists on body composition.

OBJECTIVE

We sought to assess the effect of glucocorticoids on height and body composition by comparing children with SSNS with concurrent healthy reference children. We hypothesized that chronic glucocorticoid therapy leads to obesity, decreased lean mass, and distorted distributions of fat and lean.

DESIGN

We performed a cross-sectional study of 52 subjects with SSNS (4-21 y) and 259 reference subjects. The evaluation included height, weight, and pubertal status. Fat and lean masses were assessed by dual-energy X-ray absorptiometry in all subjects. Lifetime glucocorticoid exposure was recorded for subjects with SSNS. Outcomes were expressed as SD scores (SDS).

RESULTS

Forty-one percent of subjects with SSNS were obese [body mass index (BMI) > 95th percentile], but regional fat distribution was normal. Mean total lean mass-for-height was 0.43 SD (95% CI: 0.15, 0.72) higher and mean appendicular lean mass-for-total-lean-mass was lower (-0.39 SD; 95% CI: -0.64, -0.14) in SSNS compared with reference children. The mean height-SDS in SSNS was -0.08 SD (95% CI: -0.37, 0.21) relative to national reference data, but height-SDS was significantly decreased given the degree of obesity. Height-SDS was positively associated with BMI-SDS among subjects with SSNS.

CONCLUSION

Glucocorticoid therapy for SSNS is complicated by obesity and relatively low appendicular lean mass. Overall height-SDS is normal because of a mitigating effect of elevated BMI on glucocorticoid-induced growth retardation.

Measuring nutritional status in children with chronic kidney disease

Children with chronic kidney disease (CKD) are at risk of protein-energy malnutrition. Existing clinical practice guidelines recognize this and recommend specific methods to assess nutritional status in patients with CKD. This review summarizes the methods for nutritional assessment currently recommended in the United States for children with CKD and details the strengths and limitations of these techniques in the clinical setting. Dietary assessment, serum albumin, height, estimated dry weight, weight/height index, upper arm anthropometry, head circumference, and the protein equivalent of nitrogen appearance are reviewed. We also describe methods for body-composition assessment, such as dual-energy X-ray absorptiometry, bioelectrical impedance analysis (BIA), total body potassium, densitometry, and in vivo neutron activation analysis, pointing out some advantages and disadvantages of each. In CKD, fluid overload is the most important factor leading to misinterpretation of nutritional assessment measures. Abnormalities in the distribution of fat and lean tissue may also compromise the interpretation of some anthropometric measures. In addition, metabolic abnormalities may influence the results obtained by some techniques. Issues specific to evaluating nutritional status in the pediatric population are also discussed, including normalization of nutritional measures to body size and sexual maturity. We stress the importance of expressing body-composition measures relative to height in a population in whom short stature is highly prevalent.

Quantitative high-resolution magnetic resonance imaging reveals structural implications of renal osteodystrophy on trabecular and cortical bone

PURPOSE

To explore the potential role of micro-magnetic resonance imaging (micro-MRI) for quantifying trabecular and cortical bone structural parameters in renal osteodystrophy (ROD), a multifactorial disorder of bone metabolism, traditionally evaluated by bone biopsy.

MATERIALS AND METHODS

Seventeen hemodialysis patients (average PTH level = 502 +/- 415 microg/liter) were compared with 17 age-, gender-, and body mass index (BMI)-matched control subjects. The average dialysis duration for the patients was 5.5 years (range = 0.96-18.2 years). Three-dimensional (3D) fast large-angle spin-echo (FLASE) MR images of the distal tibia (voxel size = 137 x 137 x 410 microm(3)) were processed to yield bone volume fraction (BV/TV). From a skeletonized representation of the trabecular bone network, the topology of each bone voxel was determined providing surface and curve voxel densities (SURF and CURV) and the topological erosion index (EI). Further, high-resolution two-dimensional (2D) spin-echo images were collected at the tibial midshaft for measurement of cortical bone cross-sectional area (CCA), relative CCA expressed as a percentage of total bone area (RCA), and mean cortical thickness (MCT).

RESULTS

The data show both RCA and MCT to be lower in the patients (61.2 vs. 69.1%, P = 0.008, and 4.53 vs. 5.19 mm, P = 0.01). BV/TV and SURF were lower, while EI was increased in the patients, although these differences were not quite significant (P = 0.06-0.09). All of the cortical and trabecular findings are consistent with increased bone fragility.

CONCLUSION

The data suggest that micro-MRI may have potential to characterize the structural implications of metabolic bone disease, potentially providing a noninvasive tool for the evaluation of therapies for ROD.

Long-term, high-dose glucocorticoids and bone mineral content in childhood glucocorticoid-sensitive nephrotic syndrome

BACKGROUND

Glucocorticoids suppress bone formation, impair growth, and induce obesity. We determined the effects of long-term treatment with glucocorticoids on bone mineral content in children with glucocorticoid-sensitive nephrotic syndrome, a disorder with minimal known independent effects on bone.

METHODS

We performed dual-energy x-ray absorptiometry of the whole body and spine in 60 children and adolescents with the nephrotic syndrome and 195 control subjects. We used linear regression analysis of log-transformed values to compare the bone mineral content in patients with that in controls.

RESULTS

Patients had received an average of 23,000 mg of glucocorticoids and were shorter (P=0.008) and had a greater body-mass index (P<0.001) than controls. The bone mineral content of the spine, adjusted for bone area, age, sex, degree of maturation (Tanner stage), and race, did not differ significantly between patients and controls (ratio, 0.99; 95 percent confidence interval, 0.96 to 1.02; P=0.51). After adjustment for the z score for body-mass index, the bone mineral content of the spine was significantly lower in patients than in controls (0.96; 95 percent confidence interval, 0.92 to 0.99; P=0.01). Whole-body bone mineral content, adjusted for height, age, sex, degree of maturation, and race, was significantly higher in patients than in controls (ratio, 1.11; 95 percent confidence interval, 1.05 to 1.18; P<0.001); however, the addition of the z score for body-mass index to the model eliminated the association with the nephrotic syndrome (ratio, 0.99; 95 percent confidence interval, 0.94 to 1.03; P=0.55).

CONCLUSIONS

Intermittent treatment with high-dose glucocorticoids during growth does not appear to be associated with deficits in the bone mineral content of the spine or whole body relative to age, bone size, sex, and degree of maturation. Glucocorticoid-induced increases in body-mass index were associated with increased whole-body bone mineral content and maintenance of the bone mineral content of the spine.

Obesity during childhood and adolescence augments bone mass and bone dimensions

BACKGROUND

Studies of the effect of childhood obesity on bone accrual during growth have yielded conflicting results, largely related to the failure to adequately characterize the confounding effects of growth, maturation, and body composition.

OBJECTIVE

The objective of this study was to determine the effect of childhood obesity on skeletal mass and dimensions relative to height, body composition, and maturation in males and females.

DESIGN

In 132 nonobese (body mass index < 85th percentile) and 103 obese (body mass index > or = 95th percentile) subjects aged 4-20 y, whole-body and vertebral bone mineral content (BMC) was determined by using dual-energy X-ray absorptiometry, and bone area, areal bone mineral density (BMD), and fat and lean masses were measured. Vertebral volumetric BMD was estimated as BMC/area(1.5).

RESULTS

Obesity was associated with greater height-for-age, advanced maturation for age, and greater lean mass for height (all P < 0.001). Sex-specific multivariate regressions with adjustment for maturation showed that obesity was associated with greater vertebral areal BMD for height, greater volumetric BMD, and greater vertebral BMC for bone area (all P < 0.05). After adjustment for maturation and lean mass, obesity was associated with significantly greater whole-body bone area and BMC for age and for height (all P < 0.001).

CONCLUSIONS

In contrast with the results of prior studies, obesity during childhood and adolescence was associated with increased vertebral bone density and increased whole-body bone dimensions and mass. These differences persisted after adjustment for obesity-related increases in height, maturation, and lean mass. Future studies are needed to determine the effect of these differences on fracture risk.

Interpretation of whole body dual energy X-ray absorptiometry measures in children: comparison with peripheral quantitative computed tomography

The assessment of bone health in children requires strategies to minimize the confounding effects of bone size on dual energy X-ray absorptiometry (DXA) areal bone mineral density (BMD) results. Cortical bone composes 80% of the total skeletal bone mass. The objective of this study was to develop analytic strategies for the assessment of whole body DXA that describe the biomechanical characteristics of cortical bone across a wide range of body sizes using peripheral quantitative computed tomography (pQCT) measures of cortical geometry, density (mg/mm(3)), and strength as the gold standard. Whole body DXA (Hologic QDR 4500) and pQCT (Stratec XCT-2000) of the tibia diaphysis were completed in 150 healthy children 6-21 years of age. To assess DXA and pQCT measures relative to age, body size, and bone size, gender-specific regression models were used to establish z scores for DXA bone mineral content (BMC) for age, areal BMD for age, bone area for height, bone area for lean mass, BMC for height, BMC for lean mass, and BMC for bone area; and for pQCT, bone cross-sectional area (CSA) for tibia length and bone strength (stress-strain index, SSI) for tibia length. DXA bone area for height and BMC for height were both strongly and positively associated with pQCT CSA for length and with SSI for length (all P < 0.0001), suggesting that decreases in DXA bone area for height or DXA BMC for height represent narrower bones with less resistance to bending. DXA BMC for age (P < 0.01) and areal BMD (P < 0.05) for age were moderately correlated with strength. Neither DXA bone area for lean mass nor BMC for lean mass correlated with pQCT CSA for length or SSI for length. DXA BMC for bone area was weakly associated with pQCT SSI for length, in females only. Therefore, normalizing whole body DXA bone area for height and BMC for height provided the best measures of bone dimensions and strength. DXA BMC normalized for bone area and lean mass were poor indicators of bone strength.

Bone disease in pediatric rheumatologic disorders

Children with rheumatic disorders have multiple risk factors for impaired bone health, including delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and glucocorticoid therapy. The impact of rheumatic disease during childhood may be immediate, resulting in fragility fractures, or delayed, because of suboptimal peak bone mass accrual. Recent years have seen increased interest in the effects of pediatric rheumatic disorders on bone mineralization, such as juvenile rheumatoid arthritis, systemic lupus erythematosus, and juvenile dermatomyositis. This review outlines the expected gains in bone size and mass during childhood and adolescence, and summarizes the advantages and disadvantages of available technologies for the assessment of skeletal growth and fragility in children. The varied threats to bone health in pediatric rheumatic disorders are reviewed, with emphasis on recent insights into the molecular mechanisms of inflammation-induced bone resorption. The literature assessing bone deficits and risk factors for impaired bone health in pediatric rheumatic disorders is reviewed, with consideration of the strengths and limitations of prior studies. Finally, future research directions are proposed.

Assessment of bone health in children and adolescents with cancer: promises and pitfalls of current techniques

During childhood and adolescence, skeletal development is characterized by gender-, face-, and maturation-specific increases in cortical dimensions and trabecular density. Children with cancer have multiple risk factors for impuired bone mineralization, including delayed growth and maturation, sex hormone deficiencies, decreasal physical activity and biomechanical loading of the skeleton, glucocorticoid and other immunosuppressive therapies, growth hormone deficiency, and malnutrition. This review outlines the expected gains in bone dimensions, mineral content and strength during childhood and adolescence. Varied threats to bone health in the child with cancer are summarized, with special attention to potential effects on bone formation and resorption in the growing skeleton. The strengths and limitations of dual energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT) techniques in the assessment of the different disease-related effects on bone strength are discussed, and alternative analytic approaches explored.

Calcium-free hemodialysis for hypercalcemia of malignancy in a newborn

Hypercalcemia associated with malignancy is very rare in the newborn period. Severe hypercalcemia causes neurological and cardiological disturbances and can be life threatening. Calcium-free hemodialysis has not been reported for the treatment of malignancy associated hypercalcemia in neonates. We report a 5-day-old infant with severe hypercalcemia (serum calcium 22 mg/dl) secondary to a solid tumor in the pelvis. Aggressive pharmacological treatment with furosemide, pamidronate, and calcitonin failed to reduce the serum calcium adequately. Implementation of calcium-free hemodialysis resulted in a rapid reduction of the serum calcium from 22.6 mg/dl to 11.6 mg/dl. Hemodialysis was well tolerated with no hemodynamic complications. Continuous veno-venous hemodialysis was used to maintain normocalcemia.

Long versus standard initial steroid therapy for children with the nephrotic syndromeA report from the Southwest Pediatric Nephrology Study Group

A retrospective cohort study was conducted by the Southwest Pediatric Nephrology Study Group (SPNSG) to address whether a longer initial course of corticosteroids in patients with idiopathic nephrotic syndrome (INS) provides superior protection against relapse without increased adverse effects. In order to be included in the evaluation, patients with INS must have responded to an initial steroid course, either standard or long regimen as defined here, and completed at least 1 year of follow-up. The standard regimen consisted of prednisone 2.0+/-0.3 mg/kg per day or 60+/-10 mg/m(2) per day for 28+/-4 days, followed by alternate-day prednisone for 4-12 weeks. The long regimen consisted of daily prednisone 2.0+/-0.3 mg/kg per day or 60+/-10 mg/m(2) per day for 42+/-6 days, followed by alternate-day prednisone for 6-14 weeks. The primary outcome measure was relapse of NS within 12 months of discontinuing the initial course of prednisone. There were 151 children who met the criteria for the study; 82 received the standard regimen and 69 the long regimen. The two groups did not differ in age, race, blood pressure, serum albumin, or serum cholesterol prior to the initial steroid course. The cumulative prednisone dose was 49% higher in the long regimen group than in the standard regimen group. Relapse within 12 months was reported in 72.5% of patients who received the long regimen versus 84.1% of those who received the standard regimen. The odds ratio for relapse within 12 months was 0.496 (95% confidence interval 0.22, 1.088), long versus standard regimen. This did not reach statistical significance ( chi(2)=3.058, P=0.08). The odds ratio of experiencing at least one side effect was 3.76, long relative to standard regimen ( n=133, P<0.001). Our data suggest that prolongation of the steroid treatment for the initial episode of steroid-sensitive NS may have a beneficial effect, but at the cost of increased side effects. However, definitive conclusions are limited by the retrospective design of the study and the number of patients. This may have caused failure to achieve statistical significance on the basis of a type II error.

A prospective cohort study of incident maintenance dialysis in children: an NAPRTC study

BACKGROUND

Prior studies of dialysis practices and outcomes have included children with varied duration of end-stage renal disease (ESRD). This study evaluated dialysis characteristics, complications, practices, and outcomes in an incident pediatric cohort.

METHODS

The cohort was limited to 1992 subjects enrolled in the North American Pediatric Renal Transplant Cooperative Study registry, starting hemodialysis (HD) or peritoneal dialysis (PD) between 1992 and 1998, without prior dialysis or transplantation.

RESULTS

At dialysis initiation, the median glomerular filtration rate (GFR; Schwartz formula) was 6 to 11 mL/min/1.73 m2, and 90th percentile was 14 to 25 mL/min/1.73 m2. GFR was not associated with age or race. PD was used in 97% of infants, 70 to 80% of children and 59% of adolescents. Blacks were significantly less likely to be started on PD than whites. Twenty percent of patients switched dialysis modality, largely due to infection, inadequate access or family choice. Younger children received HD almost exclusively through percutaneous catheters, while 57% of children more than six years old were dialyzed with fistula or graft after six months on HD. The prevalence of anemia (Hct <33%) still exceeded 40% after six months of dialysis. The median interval to transplantation was 1.4 years, and was significantly greater in non-white, young, and female patients. Mortality rates (deaths/1000 patient-years) varied with age, from 13.6 in infants to 2.2 in adolescents.

CONCLUSION

These data demonstrate considerable variability in patient management across pediatric centers. Prospective studies are needed to determine the optimum adequacy of care among children on dialysis and to identify populations at risk.

Decline in renal function following thoracic organ transplantation in children

Heart and/or lung transplantation are life-saving treatments for end-stage cardiopulmonary disease; however, chronic renal failure may develop. The impact of thoracic organ transplant on renal function in infants and children is not well characterized. This retrospective cohort study evaluated renal function following thoracic organ transplantation in 46 children (32 heart, 9 lung, 5 heart-lung; median age 4.1 years) with at least 12 months of follow-up. Glomerular filtration rate (GFR, ml/min/1.73 m2) was estimated by the Schwartz formula throughout and each GFR estimate was converted to per cent normal for age (GFR%). Changes in renal function following transplantation were analyzed using longitudinal mixed-effects linear regression models. GFR% decreased following thoracic organ transplantation (p <0.001). Younger age at transplant was associated with a greater decline in GFR% (p <0.01). The decline in GFR% persisted after adjustment for nutritional status with body mass index or weight-for-length z-scores. The prevalence of renal insufficiency (GFR% <75) increased from 22% at transplant to 55% and 85% at 1 and 5 years post transplant, respectively, while 15% had a GFR% <50 at 5 years post transplantation. Higher tacrolimus trough levels over the first 6 months correlated with a lower GFR% (p <0.01). Renal function declined significantly following thoracic organ transplantation.

Current concepts in pediatric bone disease

It is widely believed that osteoporosis prevention may be best accomplished during childhood and adolescence, when bones are growing rapidly and are most sensitive to environmental influences, such as diet and physical activity. For children with chronic diseases, a variety of factors may influence normal bone mineralization, including altered growth, delayed maturation, inflammation, malabsorption, reduced physical activity, glucocorticoid exposure, and poor dietary intake. In healthy children, maintaining adequate levels of calcium intake, serum vitamin D, and weightbearing physical activity may be sufficient to prevent osteoporosis later in life. Far less is known about effective prevention and treatment of poor bone mineralization in children with chronic illness, such as CF or CD. Osteoporosis prevention and intervention measures during childhood are limited by the paucity of reference data on bone mineralization. Although it is widely recognized that puberty, skeletal maturation, and body size influence BMC and bone density, no reference data for bone mineralization are scaled to these important measures. In children with chronic disease with delayed growth and maturation, the creation of such reference data is of paramount importance. In addition, the dynamic changes that occur during growth and maturation in the structural characteristics of trabecular and cortical bone and the development of the bone-muscle unit may influence current and future fracture risk. Further research is needed to characterize these changes and their use in the assessment of bone health and fracture risk in children. Only then can the impact of treatment strategies be appreciated fully.

Adverse neurologic events associated with rebound hypertension after using short-acting nifedipine in childhood hypertension

INTRODUCTION

Short-acting nifedipine (SA-NIF) is widely prescribed for acute hypertension (HTN) in children despite reports of ischemic complications in adults. We describe two children with neurologic events caused by rebound hypertension following SA-NIF use.

CASES

Patient 1 is a 7-year-old with acute nephritis and blood pressure (BP) of 185/130. She received SA-NIF which decreased BP to 114/79. When BP rebounded to 160/103, she developed severe cortical visual impairment. Head CT demonstrated edema and petechial hemorrhages in the watershed region. Patient 2 is a 10-year-old renal transplant recipient who received SA-NIF for a BP of 155/98, which resulted in a prompt decrease to 114/74. Two hours later he developed aphasia and right-sided neglect. His BP increased to 168/88 and he developed partial complex seizures. Brain MRI showed high signal intensity in the watershed areas with early gadolinium enhancement.

DISCUSSION

The temporal association of the neurologic events with the rebound increase in BP suggests a possible role for the SA-NIF, consistent with its pharmacokinetic profile. Although the adult literature has focused on the unpredictable decline in BP after SA-NIF treatment, these cases suggest that rapid increases in BP following the maximal SA-NIF effect may be associated with impaired cerebral autoregulation and encephalopathy in children. These cases underscore the need for frequent blood pressure determinations and therapy to prevent rebound hypertension.

Assessment of bone mineralization following renal transplantation in children: limitations of DXA and the confounding effects of delayed growth and development

Pediatric renal transplantation recipients have numerous risk factors for decreased bone mass, including the underlying renal disease, nutritional deficits, decreased physical activity, inflammation and exposure to steroid therapy. The assessment of bone mineralization in children following renal transplantation is fraught with difficulty. Dual energy x-ray absorptiometry (DXA) is the most commonly employed tool to assess bone mineralization. However, DXA has important limitations in children and in individuals with renal disease. This brief review will examine the expected gains in bone size and bone mass during growth and the mechanisms by which renal failure and steroid therapy interrupt these process. In addition, the limitations of DXA for detecting impaired bone mineralization in children with renal disease are reviewed and alternative approaches explored.

Variability among pediatric nephrologists in the initial therapy of nephrotic syndrome

The objective of this study was to describe the practices of North American pediatric nephrologists in treating new-onset steroid-sensitive nephrotic syndrome and impressions regarding the effect of therapy duration on the risk of relapse. A questionnaire was mailed to 130 pediatric nephrologists in the United States and Canada. One hundred and five (81%) replied. Of the respondents, 39% believed a longer steroid regimen results in more-sustained remissions; 19% did not; 18% believed perhaps, but not enough to risk the increased side-effects of the longer steroid regimen; and 24% did not know. Half of the respondents prescribed an 8-week regimen and 21% prescribed a 12-week regimen; however, in 70% of both regimens, respondents appended an additional taper. The remaining respondents either tapered at urinary remission (14%) or used another regimen (15%). Physicians using the 12-week regimen expected 44% of patients to be relapse free at 1 year, compared with 31% of patients of respondents using other regimens (P=0.005). Over the previous 5 years, 38% of respondents changed their approach; of these, 70% lengthened the treatment course. Physician perceptions and strategies did not vary according to years of clinical experience. In conclusion, there is significant variability in practice and perceptions among pediatric nephrologists; however, most have extended therapy beyond the traditional 8-week course.

Increased urinary transforming growth factor-beta(1) excretion in children with posterior urethral valves

OBJECTIVES

Patients with posterior urethral valves (PUV) are at significant risk for progression to end-stage renal disease, despite early correction of the obstruction. Experimental models of urinary obstruction demonstrate increased renal expression of the profibrotic inflammatory mediator, transforming growth factor-beta(1) (TGF-beta(1)). Urinary TGF-beta(1) excretion is elevated in certain glomerular diseases, but has not been well studied in patients with obstructive lesions. The objective of this study was to examine urinary TGF-beta(1) excretion in children with PUV.

METHODS

Fourteen patients with PUV, aged 3.2 to 14.5 years, with estimated glomerular filtration rates (GFRs) of 12.8 to 139 mL/min/1.73 m(2) were enrolled. Sixteen normal subjects (9 male, 7 female), aged 4.3 to 20.5 years, served as controls. Total urinary TGF-beta(1) concentration was assayed by enzyme-linked immunoabsorbent assay, and expressed as a ratio to urinary creatinine concentration.

RESULTS

Urinary TGF-beta(1) excretion was significantly greater in patients with PUV (range 0 to 0.063, median 0.019 ng/mg urine creatinine) compared with that of healthy controls (range 0 to 0.022, median 0.005 ng/mg urine creatinine) (P <0.01). There was no correlation between urinary TGF-beta(1) excretion and estimated GFR, past urinary diversion surgery, or bladder wall thickening. Among healthy controls, urinary TGF-beta(1) was not correlated with age or gender.

CONCLUSIONS

Results from this study suggest that TGF-beta(1) may contribute to progressive renal insufficiency in patients with PUV. Further studies are indicated to determine if agents that affect TGF-beta(1) expression, such as angiotensin-converting enzyme inhibitors, can slow the progression of renal disease in PUV.

Early risk factors for increased adiposity: a cohort study of African American subjects followed from birth to young adulthood

BACKGROUND

Obesity is an increasing concern in the United States. Effective prevention of obesity requires the risk factors to be well defined. African Americans have a high risk of obesity.

OBJECTIVE

The objective of this study was to identify risk factors, present at birth, for increased adiposity in adulthood in an African American population.

DESIGN

In this retrospective analysis of a prospective cohort study, anthropometric and socioeconomic variables were collected at birth. A representative sample of 447 African American subjects was followed up until young adulthood, when skinfold thickness was measured. Associations between the independent variables and increased adiposity (skinfold thickness above the 85th percentile) were explored by using unadjusted and adjusted analyses.

RESULTS

Three variables measured at birth were independently associated with adiposity in young adulthood, explaining 12% of the variance. The odds ratios (with 95% CIs) of these variables for increased adiposity were 2.7 (1.2, 6.2) for female sex, 4.0 (1.4, 11. 2) for first-born status, and 1.15 (1.06, 1.25) for each unit increment in maternal prepregnancy body mass index (BMI; in kg/m(2)). After adjustment for these variables, birth weight for gestational age and socioeconomic variables were not associated with adiposity.

CONCLUSIONS

This cohort study of African American subjects was the first to identify first-born status as an independent risk factor for increased adiposity in adulthood in a US population. The results of the study strengthen previous reports of the effect of female sex and maternal BMI on adulthood obesity. Identification of risk factors early in life may help target prevention toward high-risk children and allow healthy lifestyles to be established before the onset of obesity.