Extracellular Vesicles of Patients on Peritoneal Dialysis Inhibit the TGF-β- and PDGF-B-Mediated Fibrotic Processes

Among patients on peritoneal dialysis (PD), 50-80% will develop peritoneal fibrosis, and 0.5-4.4% will develop life-threatening encapsulating peritoneal sclerosis (EPS). Here, we investigated the role of extracellular vesicles (EVs) on the TGF-β- and PDGF-B-driven processes of peritoneal fibrosis. EVs were isolated from the peritoneal dialysis effluent (PDE) of children receiving continuous ambulatory PD. The impact of PDE-EVs on the epithelial-mesenchymal transition (EMT) and collagen production of the peritoneal mesothelial cells and fibroblasts were investigated in vitro and in vivo in the chlorhexidine digluconate (CG)-induced mice model of peritoneal fibrosis. PDE-EVs showed spherical morphology in the 100 nm size range, and their spectral features, CD63, and annexin positivity were characteristic of EVs. PDE-EVs penetrated into the peritoneal mesothelial cells and fibroblasts and reduced their PDE- or PDGF-B-induced proliferation. Furthermore, PDE-EVs inhibited the PDE- or TGF-β-induced EMT and collagen production of the investigated cell types. PDE-EVs contributed to the mesothelial layer integrity and decreased the submesothelial thickening of CG-treated mice. We demonstrated that PDE-EVs significantly inhibit the PDGF-B- or TGF-β-induced fibrotic processes in vitro and in vivo, suggesting that EVs may contribute to new therapeutic strategies to treat peritoneal fibrosis and other fibroproliferative diseases.

Immunosuppressive Therapy of Antibody-Mediated aHUS and TTP

The recent classification of pediatric thrombotic microangiopathies (TMA) takes into consideration mechanisms of disease for guidance to targeted therapies. We present our experience with seven patients with antibody mediated atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP). Five children had aHUS with antibodies against complement factor H (CFH-ab) and two with TTP with antibodies against metalloproteinase ADAMTS13. In the aHUS cases diagnosed and treated before the eculizumab era, CFH-ab was detected using the ELISA assay. Mutational analysis of selected complement genes was performed. TTP was diagnosed if, in addition to microangiopathic hemolytic anemia and thrombocytopenia, ischemic organ involvement and severe deficiency in ADAMTS13 activity were present. Treatment protocol consisted of plasma exchanges (PE) and steroid pulses, followed by the combination of cyclophosphamide and rituximab to achieve long-term immunosuppression. Four patients with CFH-ab and the TTP patients with ADAMTS13 antibodies came into sustained remission. After a median follow-up of 11.7 (range 7.7-12.9) years without maintenance therapy, no disease recurrence was observed; nevertheless, six patients, two had hypertension and two had proteinuria as a late consequence. One patient, with late diagnosis of CFH-ab and additional genetic risk factors who was treated only with PE and plasma substitution, reached end-stage renal disease and was later successfully transplanted using eculizumab prophylaxis. In the cases of antibody-mediated TMAs, PE and early immunosuppressive treatment may result in sustained remission with preserved kidney function. Further data are needed to establish optimal treatment of anti-FH antibody-associated HUS.

Follow-Up of Blood Pressure, Arterial Stiffness, and GFR in Pediatric Kidney Transplant Recipients

Pediatric renal transplant recipients (RTx) were studied for longitudinal changes in blood pressure (BP), arterial stiffness by pulse wave velocity (PWV), and graft function.

Patients and Methods: 52 RTx patients (22 males) were included; office BP (OBP) and 24 h BP monitoring (ABPM) as well as PWV were assessed together with glycemic and lipid parameters and glomerular filtration rate (GFR) at 2.4[1.0–4.7] (T₁) and 9.3[6.3–11.8] years (T₂) after transplantation (median [range]).

Results: Hypertension was present in 67 and 75% of patients at T₁ and T₂, respectively. Controlled hypertension was documented in 37 and 44% by OBP and 40 and 43% by ABPM. Nocturnal hypertension was present in 35 and 30% at T₁ and T₂; 24 and 32% of the patients had masked hypertension, while white coat hypertension was present in 16 and 21% at T₁ and T₂, respectively. Blood pressure by ABPM correlated significantly with GFR and PWV at T₂, while PWV also correlated significantly with T₂ cholesterol levels. Patients with uncontrolled hypertension by ABPM had a significant decrease in GFR, although not significant with OBP. Anemia and increased HOMAi were present in ~20% of patients at T₁ and T₂.

Conclusion: Pediatric RTx patients harbor risk factors that may affect their cardiovascular health. While we were unable to predict the evolution of renal function based on PWV and ABPM at T₁, these risk factors correlated closely with GFR at follow-up suggesting that control of hypertension may have an impact on the evolution of GFR.

FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy

Background

Factor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.

Methods

A total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).

Results

Eight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.

Conclusions

Our observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G.

Prognostic Value of Early Risk Stratification in Pediatric Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a life-threatening disease with risk stratification-based treatment strategy in adults. Although the risk factors have been studied individually in children, effective risk stratification is still lacking. We have tested the prognostic accuracy of pediatric PAH risk factors in our patient group.

PATIENTS AND METHODS

Records of 58 PAH patients treated between 1995 and 2019 were reviewed retrospectively. Median age at diagnosis was 4.2 years (range, 0.1-16.1 years), and follow-up was 5.4 years (range, 0.01-24.1 years). Data collected at diagnosis were demographics, World Health Organization functional class, evidence of right ventricular failure, and parameters of echocardiography and cardiac catheterization.

RESULTS

Mortality was 29% and 33% reached the composite endpoint. Patients with idiopathic PAH (n = 12) had increased risk of mortality compared with the congenital heart disease-associated PAH group (n = 32) (P = .0024). Neither the initial World Health Organization functional class staging nor the echocardiographic parameters significantly predicted the prognosis. The number of risk factors had no significant prognostic value either. In contrast, patients with higher pulmonary vascular resistance index (PVRI) had significantly increased risk (each 10 Wood units ⋅ m² increase in PVRI being associated with 49.1% higher hazard, P = .0048).

CONCLUSIONS

Survival analysis showed that PAH etiology might be an important determinant in pediatric PAH risk stratification. We confirmed that PVRI has predictive value in prognostic assessment. We could not establish the prognostic value of nonweighted single risk factors or their combination to predict pediatric PAH outcome due to the low sample size, but these results indicate that such studies are warranted.

C4 nephritic factor in patients with immune-complex-mediated membranoproliferative glomerulonephritis and C3-glomerulopathy

BACKGROUND

Acquired or genetic abnormalities of the complement alternative pathway are the primary cause of C3glomerulopathy(C3G) but may occur in immune-complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) as well. Less is known about the presence and role of C4nephritic factor(C4NeF) which may stabilize the classical pathway C3-convertase. Our aim was to examine the presence of C4NeF and its connection with clinical features and with other pathogenic factors.

RESULTS

One hunfe IC-MPGN/C3G patients were enrolled in the study. C4NeF activity was determined by hemolytic assay utilizing sensitized sheep erythrocytes. Seventeen patients were positive for C4NeF with lower prevalence of renal impairment and lower C4d level, and higher C3 nephritic factor (C3NeF) prevalence at time of diagnosis compared to C4NeF negative patients. Patients positive for both C3NeF and C4NeF had the lowest C3 levels and highest terminal pathway activation. End-stage renal disease did not develop in any of the C4NeF positive patients during follow-up period. Positivity to other complement autoantibodies (anti-C1q, anti-C3) was also linked to the presence of nephritic factors. Unsupervised, data-driven cluster analysis identified a group of patients with high prevalence of multiple complement autoantibodies, including C4NeF.

CONCLUSIONS

In conclusion, C4NeF may be a possible cause of complement dysregulation in approximately 10-15% of IC-MPGN/C3G patients.

Validation of distinct pathogenic patterns in a cohort of membranoproliferative glomerulonephritis patients by cluster analysis

Background

A novel data-driven cluster analysis identified distinct pathogenic patterns in C3-glomerulopathies and immune complex-mediated membranoproliferative glomerulonephritis. Our aim was to replicate these observations in an independent cohort and elucidate disease pathophysiology with detailed analysis of functional complement markers.

Methods

A total of 92 patients with clinical, histological, complement and genetic data were involved in the study, and hierarchical cluster analysis was done by Ward method, where four clusters were generated.

Results

High levels of sC5b-9 (soluble membrane attack complex), low serum C3 levels and young age at onset (13 years) were characteristic for Cluster 1 with a high prevalence of likely pathogenic variations (LPVs) and C3 nephritic factor, whereas for Cluster 2—which is not reliable because of the small number of cases—strong immunoglobulin G staining, low C3 levels and high prevalence of nephritic syndrome at disease onset were observed. Low plasma sC5b-9 levels, decreased C3 levels and high prevalence of LPV and sclerotic glomeruli were present in Cluster 3, and patients with late onset of the disease (median: 39.5 years) and near-normal C3 levels in Cluster 4. A significant difference was observed in the incidence of end-stage renal disease during follow-up between the different clusters. Patients in Clusters 3–4 had worse renal survival than patients in Clusters 1–2.

Conclusions

Our results confirm the main findings of the original cluster analysis and indicate that the observed, distinct pathogenic patterns are replicated in our cohort. Further investigations are necessary to analyse the distinct biological and pathogenic processes in these patient groups.

Analysis of Linear Antibody Epitopes on Factor H and CFHR1 Using Sera of Patients with Autoimmune Atypical Hemolytic Uremic Syndrome

Introduction

In autoimmune atypical hemolytic uremic syndrome (aHUS), the complement regulator factor H (FH) is blocked by FH autoantibodies, while 90% of the patients carry a homozygous deletion of its homolog complement FH-related protein 1 (CFHR1). The functional consequence of FH-blockade is widely established; however, the molecular basis of autoantibody binding and the role of CFHR1 deficiency in disease pathogenesis are still unknown. We performed epitope mapping of FH to provide structural insight in the autoantibody recruitment on FH and potentially CFHR1.

Methods

Eight anti-FH positive aHUS patients were enrolled in this study. With overlapping synthetic FH and CFHR1 peptides, we located the amino acids (aa) involved in binding of acute and convalescence stage autoantibodies. We confirmed the location of the mapped epitopes using recombinant FH domains 19–20 that carried single-aa substitutions at the suspected antibody binding sites in three of our patients. Location of the linear epitopes and the introduced point mutations was visualized using crystal structures of the corresponding domains of FH and CFHR1.

Results

We identified three linear epitopes on FH (aa1157–1171; aa1177–1191; and aa1207–1226) and one on CFHR1 (aa276–290) that are recognized both in the acute and convalescence stages of aHUS. We observed a similar extent of autoantibody binding to the aHUS-specific epitope aa1177–1191 on FH and aa276–290 on CFHR1, despite seven of our patients being deficient for CFHR1. Epitope mapping with the domain constructs validated the location of the linear epitopes on FH with a distinct autoantibody binding motif within aa1183–1198 in line with published observations.

Summary

According to the results, the linear epitopes we identified are located close to each other on the crystal structure of FH domains 19–20. This tertiary configuration contains the amino acids reported to be involved in C3b and sialic acid binding on the regulator, which may explain the functional deficiency of FH in the presence of autoantibodies. The data we provide identify the exact structures involved in autoantibody recruitment on FH and confirm the presence of an autoantibody binding epitope on CFHR1.

Decreased Neutrophil Extracellular Trap Degradation in Shiga Toxin-Associated Haemolytic Uraemic Syndrome

BACKGROUND

Neutrophil extracellular traps (NETs) can stimulate thrombosis, and their degradation is decreased in several autoimmune disorders. It was recently reported that some patients with haemolytic uraemic syndrome (HUS) also fail to degrade NETs and that neutrophils from Shiga toxin-associated HUS are primed to form NETs.

METHOD

We used a well-characterized cohort of 74 thrombotic microangiopathy (TMA) patients, with a subset also providing follow-up samples, and 112 age-matched controls to investigate NET degradation and serum nuclease activity in TMA before, during and after treatment.

RESULTS

We identified that in the cohort of TMA patients, 50% of patients with Shiga toxin-associated HUS displayed a decreased ability to degrade NETs. NET degradation correlated with serum nuclease activity, but not with autoantibodies against double-stranded DNA, which has been previously observed in some autoimmune disorders. Further, NET degradation negatively correlated with serum creatinine levels, suggesting that kidney function was negatively impacted by the low NET degradation ability.

CONCLUSIONS

We revealed that decreased NET degradation is a common feature of Shiga toxin-associated HUS and that it is associated with decreased kidney function in these patients. It remains to be clarified whether improving NET degradation would be beneficial for the patient.

Bone metabolism and arterial stiffness after renal transplantation

BACKGROUND/AIMS

To assess the relationship between bone and vascular disease and its changes over time after renal transplantation. Metabolic bone disease (MBD) is common in chronic kidney disease (CKD) and is associated with cardiovascular (CV) disease. Following transplantation (Tx), improvement in CV disease has been reported; however, data regarding changes in bone disease remain controversial.

METHODS

Bone turnover and arterial stiffness (pulse wave velocity (PWV)) were assessed in 47 Tx patients (38 (3-191) months after Tx).

RESULTS

Bone alkaline phosphatase (BALP), osteocalcin (OC) and beta-crosslaps were significantly higher in Tx patients, and decreased significantly after one year. There was a negative correlation between BALP, OC and steroid administered (r = -0.35; r = -0.36 respectively). PWV increased in the Tx group (1.15 SD). In patients with a follow up of <24 months, PWV was correlated with BALP and beta-crosslaps (r=0.53; r = 0.69 respectively) while in the ≥24 months group, PWV was correlated with cholesterol (r=0.38).

CONCLUSIONS

Increased bone turnover and arterial stiffness are present following kidney transplantation. While bone turnover decreases with time, arterial stiffness correlates initially with bone turnover, after which the influence of cholesterol becomes significant. Non-invasive estimation of bone metabolism and arterial stiffness may help to assess CKD-MBD following renal transplantation.

The role of complement in Streptococcus pneumoniae-associated haemolytic uraemic syndrome

BACKGROUND

Atypical forms of haemolytic uraemic syndrome (aHUS) include HUS caused by defects in the regulation of alternative complement pathway and HUS linked to neuraminidase-producing pathogens, such as Streptococcus pneumoniae. Increasing data support a pathogenic role of neuraminidase in the development of S. pneumoniae-associated haemolytic uraemic syndrome (SP-HUS), but the role of complement has never been clarified in detail. Therefore, we aimed to investigate whether the pathologic complement profile and genetic risk factors of aHUS are present in patients with SP-HUS.

METHODS

Enrolling five patients with SP-HUS classical and alternative pathway activity, besides C3, C4, factors H, B, I and anti-factor H autoantibody levels were determined. The coding regions of CFH, CFI, CD46 (MCP), THBD, C3 and CFB genes were sequenced and the copy number of CFI, CD46, CFH and related genes were also analyzed.

RESULTS

We found that in the acute phase samples of SP-HUS patients, complement components C4, C3 and activity of the classical and alternative pathways were decreased, indicating severe activation and complement consumption, but most of these alterations normalized later in remission. Three of the patients carried mutations and risk haplotypes in complement-mediated aHUS associated genes. The identified mutations include a previously published CFI variant (P50A) and two novel ones in CFH (R1149X) and THBD (T44I) genes.

CONCLUSIONS

Our results suggest that severe complement dysregulation and consumption accompany the progress of invasive pneumococcal disease (IPD)-associated SP-HUS and genetic variations of complement genes may contribute to the development of this complication in a proportion of the affected patients.

Complement activation in thrombotic thrombocytopenic purpura

BACKGROUND

Ultra-large von Willebrand factor and deficiency of its cleaving protease are important factors in the events leading to thrombotic microangiopathy; however, the mechanisms involved are only partly understood. Whereas pathological activation of the alternative complement pathway is linked to atypical hemolytic uremic syndrome, the role of complement activation in thrombotic thrombocytopenic purpura (TTP) is unknown. The aim of this study was to investigate whether signs of complement activation are characteristic of TTP.

PATIENTS AND METHODS

Twenty-three patients with TTP (18 women, median age 38 years) and 17 healthy controls (13 women, median age 38 years) were included. Complement parameters (C3, Factors H, I, B and total alternative pathway activity) together with complement activation fragments (C3a) or complexes (C1rs-INH, C3bBbP, sC5b9) were measured by ELISA or RID. ADAMTS13 activity and anti-ADAMTS13 inhibitory antibodies were measured by the VWF-FRET73 assay.

RESULTS

Increased levels of C3a, and SC5b9 were observed in TTP during acute episodes, as compared with healthy controls. Decreased complement C3 levels indicative of complement consumption occurred in 15% of acute TTP patients. Significant decrease of complement activation products C3a and SC5b9 was observed during plasma exchange (PEX). The sustained presence of anti-ADAMTS13 inhibitory antibodies in complete remission was associated with increased complement activation.

CONCLUSION

These data document in an observational study the presence of complement activation in TTP. Further investigation is needed to determine its potential pathogenetic significance.

Effects of bone and mineral metabolism on arterial elasticity in chronic renal failure

Arterial stiffness (Ast) individually predicts cardiovascular (CV) mortality. Ast increases via vascular calcification and can be characterized by pulse wave velocity (PWV). We assessed the influence of mineral and bone metabolism on Ast in dialyzed (D) and renal transplanted (Tx) children by measuring fetuin-A and bone markers [bone-specific alkaline phosphatase (BALP); beta-CrossLaps (beta)]. Normalized PWV/height (PWV/h) of 11 D and 17 Tx patients was measured by applanation tonometry. Levels of calcium (Ca), phosphate (P), fetuin-A, and bone markers were analyzed. Ca x P/fetuin-A ratio was calculated to characterize the balance of calcification and inhibition. Cumulative dose of calcitriol was also assessed. Fetuin-A was lower in D and Tx compared with healthy controls. Bone markers and Ca x P/ fetuin-A of D were significantly higher than those of Tx and controls. In D PWV/h correlated with Ca x P/fetuin-A and BALP (r=0.8; p=0.005, r=0.6, p=0.05, respectively); BALP correlated with Ca x P/fetuin-A (r=0.7, p=0.01). In Tx, there was a correlation between calcitriol administered before transplantation and PWV/h (r=0.5, p=0.04). Increased bone turnover was coupled with an increased potential of calcium-phosphate precipitation, as shown by the increased Ca x P/fetuin-A. It might explain the connection between disturbed mineral and bone metabolism and Ast. Tx might be beneficial on Ast, though follow-up studies are needed.

Post-transplant diabetes mellitus in children following renal transplantation

PTDM plays a role in chronic allograft nephropathy and decreases graft and patient survival. Considering the serious outcome of chronic hyperglycemia, the importance of early recognition and the few data in children, in this retrospective analysis we studied the characteristics and risk factors of PTDM in 45 pediatric renal transplant recipients receiving Tac or CyA-based immunosuppression. Fasting blood sampling and OGTT were performed. PTDM has been developed in six patients (13%), while seven children (16%) had IGT, with the overall incidence of a glucose metabolic disorder of 29% in pediatric renal transplants. Patients in the PTDM + IGT group were younger and had higher systolic blood pressure and serum triglyceride level than children with normal glucose tolerance. Multivariate analysis identified Tac treatment, Tac trough level, steroid pulse therapy and family history of diabetes to be associated with the onset of PTDM. In pediatric renal transplants, OGTT and frequent assessment of blood glucose levels might be essential not only in the post-transplant management, but also prior to transplantation, particularly with family history of diabetes. Careful monitoring and modified protocols help to minimize the side effects of Tac and corticosteroids.

Pulse wave velocity in end-stage renal disease: influence of age and body dimensions

Arterial stiffness increases with age. This process is accelerated by end-stage renal disease (ESRD). Pulse wave velocity (PWV) increases with arterial stiffness. In this study, PWV of 133 healthy individuals (6-23 y of age) and 11 patients on dialysis was measured to establish the normal values of PWV and to compare them with those in ESRD. Age-matched (A-C) and height- and weight-matched (H/W-C) control groups were used. Thereafter, PWV was indexed to height and the data were reevaluated. The role of the risk factors including serum calcium, phosphate, parathyroid hormone (PTH), and the time on dialysis was analyzed using a score system. PWV correlated with age, weight, height, blood pressure, and heart rate. ESRD patients were smaller than A-C and older than H/W-C. PWV of patients with ESRD did not differ from A-C; however, it was elevated in comparison to H/W-C. In both healthy and ESRD patients, the PWV/height ratio was independent of age. PWV/height was increased in ESRD. There was a correlation between PWV/height and the risk factor score. Controls matched for height and weight or PWV/height should be used in cases of growth failure. A number of risk factors responsible for increased arterial stiffness are present in ESRD.

Determinants of baroreflex function in juvenile end-stage renal disease

Arterial baroreflex sensitivity (BRS) is markedly reduced in middle-aged patients with end-stage renal disease (ESRD), due to the combined effects of aging, arterial stiffening, and autonomic neuropathy. Much less is known about the effects of ESRD on arterial baroreflex in juvenile patients. Therefore, we investigated baroreflex function and its relation to carotid artery elasticity and heart rate variability in children and young adults with ESRD. We studied 42 subjects (9-30 years): 14 patients on maintenance hemodialysis (HD), 14 renal transplant recipients (RT), and 14 healthy control subjects (C). Baroreflex function was determined by pharmacological (BRS) and spontaneous (sequence and spectral indices) techniques. Carotid artery elasticity was characterized by stiffness index beta. Heart rate variability was assessed using time and frequency domain measures. Data are expressed as mean+/-s.d. BRS was markedly reduced in HD as compared to C (10.0+/-4.2 vs 25.7+/-5.9 ms/mm Hg); spontaneous indices were reduced to similar extent. Carotid artery stiffness was approximately 50% higher in HD than in C and was inversely related to BRS. Heart rate variability was also compromised in HD, and was directly related to spontaneous indices. No significant differences existed in any of these variables between RT and C. Decreased baroreflex function in juvenile HD is partly due to loss of carotid artery elasticity and partly due to impaired heart rate variability. Renal transplantation may partly prevent impairment or improve compromised baroreflex function in young patients with ESRD.

Effect of propranolol on heart rate variability in patients with end-stage renal disease: a double-blind, placebo-controlled, randomized crossover pilot trial

BACKGROUND

Low heart rate variability (HRV) is an independent risk factor of cardiac mortality in patients with end-stage renal disease (ESRD). It has been explained by uremic parasympathetic neuropathy. Sympathetic overactivity can also reduce HRV. Our aim was to determine whether there is vagal activity in ESRD patients that is masked by sympathetic activity.

METHODS

The effect of propranolol on HRV was examined in 13 patients with ESRD, aged 20.1 +/- 7.6 years without diabetes. All patients were given intravenous propranolol (0.05 mg/kg) once and placebo once in a randomized, double-blind way, with an interval of 6.6 days (mean, range: 2-9). Propranolol was administered before hemodialysis treatment, after 40 minutes supine resting period. HRV was registered for 10 minutes, during supine, before and after the injection. Patients' HRV data were compared to that of 29 age-matched healthy controls.

RESULTS

Initially, both high-(HFV) and low-frequency (LFV) bands of heart rate variability were lower in ESRD patients compared to controls (p < 0.001 for both). Propranolol resulted in a significant increase of HFV (propranolol: AlgHFV = 0.182 (0.027 - 0.337), placebo: deltalgHFV = -0.029 (-0.128 - +0.070); p = 0.032). Elevation of LFV was not significant. Six patients had an elevated plasma norepinephrine and/or epinephrine level. Plasma dopamine level was elevated in all but 1 patient (mean: 432 pmol/l, 95% CI: 320-543) and showed an inverse relationship with the increase of IgHFV secondary to propranolol (r = -0.66, p = 0.014).

CONCLUSIONS

Low HFV of ESRD patients can be improved by beta-adrenergic blockade. It demonstrates that there is some vagal activity in ESRD that is masked by sympathetic activity. Therefore, altered sympathovagal balance of ESRD patients should be taken into consideration in the assessment of vagal uremic neuropathy.

Autonomic dysfunction in uremia assessed by heart rate variability

Decreased heart rate variability is an independent risk factor for cardiac mortality in hemodialysis patients. Our aim was to determine whether it is already present in uremic children and young adults on hemodialysis and following renal transplantation. Twenty-two hemodialysis patients [age 17.2 years (median, quartiles 13.0-22.6)], 22 transplant patients [18.4 years (14.4-21.2)], and 29 healthy controls [16.4 years (15.7-21.1)] were examined. Heart rate and its high (HF) and low (LF) frequency variability were measured in the supine position for 10 min. High and low frequency variability was significantly reduced, whereas heart rate and LF/HF ratio was significantly elevated in both patient groups compared with controls. There was a clear-cut difference between the dialyzed and the transplanted groups based on the HF variability, with the lowest values in the dialysis group ( P<0.01). LF and LF/HF data did not allow us to distinguish between the patient groups. In conclusion, heart rate variability in the HF range is a sensitive tool for detecting cardiovascular autonomic dysfunction that is already present in children and adolescents with impaired kidney function.

Hyperhomocysteinaemia and MTHFR C677T gene polymorphism in renal transplant recipients

AIM

To study the effect of folate treatment on hyperhomocysteinaemia and the effect of 5,10-methylenetetrahydrofolate reductase (MTHFR) gene polymorphism on total homocysteine and folate concentrations after renal transplantation.

METHODS

A total of 30 transplanted children and adolescents were investigated for total homocysteine and folate serum concentrations before and after folate treatment, as well as for the presence of the MTHFR C677T polymorphism.

RESULTS

The allele frequency of C677T polymorphism in the MTHFR gene in the study population (0.33) was not different to that in controls (0.38). Before folate treatment the homocysteine concentration was raised in all groups; following folate supplementation it was significantly decreased in the CC and CT groups, but not in the TT group. In patients with CC genotype, serum homocysteine correlated with serum creatinine and cholesterol, and time since transplantation before treatment.

CONCLUSION

Folate supplementation appears to be an effective strategy to normalise total homocysteine concentration in renal transplanted children and adolescents.

Signs of autonomic neuropathy in childhood uremia

To evaluate the presence of autonomic neuropathy in childhood uremia, cardiovascular autonomic reflexes were examined in children with chronic renal failure. Cardiovascular autonomic reflexes of 10 uremic patients on chronic dialysis and 10 transplanted patients were compared to assess the effect of transplantation on autonomic neuropathy. Resting heart rate, heart rate changes induced by deep breathing, by Valsalva maneuver, and following standing up, and blood pressure change induced by handgrip test were examined. Of the 10 uremic children, 4 showed early involvement and 2 had definite involvement of autonomic neuropathy. Only 1 of the 10 transplanted patients showed early signs of autonomic neuropathy. Autonomic tests demonstrated predominantly parasympathetic dysfunction. In conclusion, cardiovascular autonomic neuropathy is not rare in children and adolescents and young adults with chronic renal failure. In contrast, the prevalence is very low in transplanted patients with similar uremic precedents. Efforts should be made to prevent or delay this uremia-related complication.

Monitoring cardiovascular changes during hemodialysis in children

Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 years) and 11 healthy children were investigated for basic circulatory parameters. Thoracic impedance (Zo) and circulatory parameters were monitored by impedance cardiography (ICG) during HD. Erythrocyte Na+/K+ATP-ase and EDLF were measured before and after HD. Up to the loss of 6% of total body weight, Zo rose linearly with fluid removal, above this no further increase occurred. Heart rate and mean arterial pressure (MAP) were inversely related (r = -0.97); MAP rose in the first and decreased in the second part of HD. Systemic vascular resistance paralleled MAP, whereas stroke volume rapidly decreased, but stabilized in the second part of HD. The ratio of preejection period/ventricular ejection time (PEP/VET) correlated positively with HD duration (r = 0.92), suggesting diminished cardiac filling. Cardiac index (CI) remained stable. EDLF was high in uremia accompanied by depressed Na+/K+ATP-ase (P < 0.05 and P < 0.01, respectively). Following HD Na+/K+ATP-ase normalized. Correlation between Na+/K+ATP-ase activity and MAP was linear (r = 0.85). In conclusion, ICG during HD provides detailed information concerning circulatory adaptation resulting in stable CI, suggesting that the dialysis-induced hypovolemia is compensated by the centralization of the blood volume. Changes of Na+/K+ATP-ase indicate that dialyzable blood pressure-regulating substance(s) inhibit(s) the pump. However, lack of further correlation between Na+/K+ATP-ase, EDLF, and cardiovascular parameters indicates the complexity of the regulatory processes.

Higher osteocalcin levels and cross-links excretion in young men born with low birth weight

As the result of accelerated growth, the final height of infants born with low birth weight (LBW) is near to the normal. Limited data are available about the bone density and bone turnover just after completion of skeletal development. We have investigated the bone turnover and bone density in 49 apparently healthy young LBW men (age 19-21 years; 21 born small for gestational age (SGA) and 28 appropriate for gestational age (AGA)) and in 16 age-matched controls. Bone mineral density of lumbar spine, femoral neck, and radius midshaft, the markers of calcium homeostasis, biochemical parameters of bone turnover as serum osteocalcin (OC), and urinary pyridinoline (PYD) and deoxypyridinoline (DPD) levels were measured. Bone mineral densities of LBW subjects were not altered. Serum calcium (SGA: 2.44+/-0.15; AGA:2.41+/-0.17, control: 2.25+/-0.09 mmol/liter, P < 0.05), OC (SGA:23.4+/-9.9; AGA:20.8+/-7.6; control:13.3+/-4.6 ng/ml, P < 0.01), total alkaline phosphatase (AP) (SGA:201+/-61; AGA:193+/-81, control: 117+/-34 IU/liter, P < 0.01), and urinary DPD/creat (ln.values: SGA:3.10+/-0.48; AGA:3.17+/-0.46; control:2.58+/-0.57 nmol/mmol, P < 0.05) were higher, whereas fractional excretion of calcium (SGA:0.94+/-0.470; AGA: 1.03+/-0.51, control:1.31+/-0.75%, P < 0.05) was lower in both SGA and AGA groups. PTH and 25OHD were not different. Significant correlation was obtained between seCa, OC, AP, DPD and birth weight of the subjects, but feCa correlated inversely to the birth weight. It was concluded that the bone turnover of LBW men is accelerated, but well balanced in young adulthood. Further investigation is needed to describe the possible link between accelerated bone turnover and hormonal homeostasis of LBW subjects.

Normal kidney function and elevated natriuresis in young men born with low birth weight

The aim of our study was to characterize renal function and its relationship to blood pressure in healthy young Caucasian men born with a birth weight under 2,500 g (LBW). Urinary protein patterns, N-acetylglucosamine and gamma-glutamyltransferase activities, fractional sodium and potassium excretions, glomerular filtration rate, blood pressure, and erythrocyte Na+/K+-ATPase activities were determined in 65 subjects, of whom 49 were born with LBW. Signs of glomerular or tubular damage were not detected in the LBW population. However, the blood pressure and the renal sodium excretion were inversely correlated to the subjects' birth weight and were higher in LBW subjects than in controls. In contrast, the erythrocyte Na+/K+-ATPase activities were lower in LBW subjects. An inverse correlation was detected between the subjects' Na+/K+-ATPase activities and the renal sodium excretion or blood pressure. In summary, our results suggest that: (1) in young LBW Caucasian males signs of early glomerular and tubular impairment are not present; (2) the elevated renal sodium excretion may be a result of higher blood pressure; (3) the alteration of Na+/K+-ATPase activity might play a role either in the elevation of blood pressure and/or in the enhanced natriuresis of LBW subjects.

Bone metabolism and mineral density following renal transplantation

AIM

To study bone turnover following renal transplantation using a panel of biochemical markers and to correlate the results with both areal and volumetric bone mineral density (BMD).

PATIENTS

A total of 31 patients aged 18.1 years were transplanted 5.4 years before this study. Control patients (n = 31) were age and gender matched.

METHODS

In addition to measurement of biochemical markers, BMD was measured by single photon absorptiometry and peripheral quantitative computed tomography on the non-dominant radius.

RESULTS

Patients had reduced glomerular filtration rate, raised concentrations of serum phosphate, serum procollagene type I carboxy terminal propeptide, osteocalcin, and serum procollagene type I cross linked carboxy terminal telopeptide. The differences were still significant if only patients with normal intact parathyroid hormone were considered. BMD single photon absorptiometry Z score for age was significantly decreased. Following standardisation for height the differences were no longer present. With volumetric techniques patients had normal trabecular but decreased cortical and total BMD compared to age matched controls, but there was no difference from height matched controls.

CONCLUSION

Markers of bone turnover are increased following renal transplantation. However, the biochemical analysis did not allow conclusions to be drawn on the bone mineral content. BMD single photon absorptiometry Z score corrected for height and BMD measured by quantitative computed tomography compared to height matched controls were normal in paediatric renal transplantation patients. Height matched controls should be used in both areal and volumetric BMD measurements in states of growth failure.

Sodium-lithium countertransport in children with nephrotic syndrome

The mechanisms of sodium retention in edema-forming minimal change nephrotic syndrome (MCNS) have not been completely evaluated. The aim of this study was to characterize the transmembrane sodium transport in nephrotic syndrome by measuring the erythrocyte sodium-lithium countertransport (SLC) in vitro. Eighteen children with MCNS were studied in the edema-forming state, and subsequently at the beginning of remission. Nephrotic children with edema retained sodium (10+/-12 micromol/day) and had a higher SLC [426+/-118 vs. 281+/-60 micromol/l red blood cells (RBC) per hour, P=0.003). The intracellular sodium concentration of nephrotics was 6.1+/-2.1 mmol/l RBC, which did not differ from that of controls (6.42+/-2.24, n=13). In remission sodium balance became negative (-30+/-21 mmol/day), and the SLC decreased but still differed significantly from control values (P=0.009). The intracellular sodium content decreased to 4.4+/-0.9 mmol/l RBC (P=0.002). There was a negative correlation between erythrocyte SLC and plasma albumin concentration (r=0.48, P=0.003), and urinary sodium excretion rate (r=0.66, P=0.001). In conclusion, erythrocyte SLC is high in the edema-forming state of childhood nephrotic syndrome and decreases with the onset of remission. A role for the SLC in the altered sodium homeostasis of nephrotic syndrome is suggested.

Sodium transport and bone mineral density in hypercalciuria with thiazide treatment

Erythrocyte sodium-potassium (Na+/K+)-ATPase and sodium-lithium (Na+/Li+) countertransport activities were measured in 18 children (aged 9.6 years, range 6-16 years) with idiopathic hypercalciuria (IHU) to evaluate cellular Na handling. The effect of chronic thiazide administration on these parameters and on bone mineral density was also evaluated. Patients with IHU had significantly lower erythrocyte Na+/K+-ATPase activity than 23 age-matched healthy controls (mean +/- SEM 2,156 +/- 110 micromol P/l erythrocyte per hour vs. 3,165 +/- 175, P < 0.01). Thiazide treatment significantly lowered urinary calcium excretion; this was followed by a slight suppression of intact parathyroid hormone (iPTH). The urinary calcium/creatinine ratio before and during treatment was 0.90 +/- 0.07 mmol/mmol versus 0.51 +/- 0.06 respectively, P < 0.01. The corresponding iPTH levels were 5.9 +/- 0.6 pmol/l and 5.1 +/- 0.7, P < 0.05. The Na+/K+-ATPase activity increased significantly (2,769 +/- 169 micromol P/l erythrocyte per hour vs. 2,156 +/- 110 in the control period, P < 0.01) and the Na+/Li+ countertransport decreased (268 +/- 28 micromol Li/l erythrocyte per hour vs. 328+26 in the control period, P < 0.03). The bone mineral density Z score rose from -1.3 +/- 0.26 to -0.8 +/- 0.22 (P < 0.03). We conclude that IHU is accompanied by abnormalities of erythrocyte Na+/K+-ATPase and Na+/Li+ countertransport which are corrected by chronic hydrochlorothiazide administration. These changes could model alterations in renal tubular transport mechanisms still to be elucidated. Chronic thiazide treatment also has a positive effect on bone mineral density.

X-linked hypophosphatemia: effects of treatment with recombinant human growth hormone

The impact of recombinant human growth hormone (rhGH) treatment on growth, bone mineral metabolism, and bone mineral density (BMD) was evaluated in six children (3 girls, 3 boys) with familial hypophosphatemic rickets (XLH). Five were prepubertal (aged 6-8.8 years), one 15.3-year-old boy had combined XLH and GH deficiency, but had not been treated with rhGH previously. rhGH was administered daily for 1 year, at a dose of 1 IU/kg per week, combined with 1,25-dihydroxyvitamin D3 and oral phosphate therapy. Z scores for growth velocity and height improved significantly (-2.9 vs. 2.5, P < 0.01, and -2.2 vs. -1.5, P < 0.01, respectively). However, the ratio of Z score for height to that of subischial leg length decreased significantly (0.65 vs. 0.43, P < 0.01), indicating disproportionate growth in favor of the trunk. The height-corrected BMD Z increased slightly (-0.99 vs. -0.94, P < 0.05). A slight increase in serum phosphate occurred (0.78 vs. 0.88 mmol/l, P < 0.02). Tubular reabsorption of phosphate/glomerular filtration rate increased from 0.45 mmol/l to 0.55 mmol at 6 months (P < 0.02), but returned to the initial level at 12 months. These results indicate that children with XLH can benefit from the positive effect of rhGH on growth, however treatment could aggravate the already existing tendency to disproportionate growth. GH production should be evaluated in poorly growing patients with XLH, because it can mask GH deficiency. rhGH can be safely combined with conventional treatment in XLH. Further studies are needed to determine the effect of treatment on final height and maximal BMD.

Oscillometric twenty-four-hour ambulatory blood pressure values in healthy children and adolescents: a multicenter trial including 1141 subjects

Ambulatory blood pressure (ABP) monitoring is increasingly used to evaluate the blood pressure of children and adolescents. The upper normal ABP values in the pediatric age group are still unknown, because reference values based on a sufficiently high number of healthy children have not yet been published. In this multicenter trial, we pooled ABP records of 1141 healthy children and adolescents with a body height between 115 and 185 cm. The study was carried out by seven centers according to a common protocol. The 50th percentile for 24-hour systolic ABP increased moderately with height, from 103 to 113 mm Hg in girls and from 105 to 120 mm Hg in boys. The 50th percentile for diastolic 24-hour means was 66 +/- 1 mm Hg, irrespective of height or gender. Diastolic daytime means were 73 +/- 1 mm Hg, which is remarkably high compared with reference values for casual blood pressure. The mean nocturnal systolic and diastolic ABP (midnight to 6 AM) was 13% +/- 6% and 23% +/- 9% lower compared with the daytime means (8 AM to 8 PM), respectively. This multicenter study provides well-based limits of normal ABP in mid-European children.

Urinary calcium and oxalate excretion in children

We have established normal values for calcium/creatinine (Ca/Cr) and oxalate/creatinine (Ox/Cr) ratios in 25 infants (aged 1-7 days) and 391 children (aged 1 month to 14.5 years) and compared these with values obtained in 137 children with post-glomerular haematuria and 27 with nephrolithiasis. Oxalate was measured by ion chromatography. Nomograms of Marshall and Robertson were used to calculate urine saturation to calcium oxalate. The Ca/Cr ratio was normally distributed whereas the Ox/Cr ratio had a log-normal distribution. The molar ratio of Ca/Cr was the lowest in the first days of life and the highest between 7 month and 1.5 years (mean +/- SD = 0.39 +/- 0.28 mmol/mmol). Following a slight decrease it stabilised by the age of 6 years (0.34 +/- 0.19 mmol/mmol). The highest Ox/Cr values were measured during the 1st month of life [geometric mean 133 (range 61-280) mumol/mmol], followed by a gradual decrease until 11 years of age [mean 24 (range 6-82) mumol/mmol]. Thirty-six haematuric children had hypercalciuria (26%), 23 had absorptive hypercalciuria, 13 renal type. Children with absorptive hypercalciuria on a calcium-restricted diet had significantly higher oxalate excretion than those with renal hypercalciuria and the control group [38 (range 28-49) vs. 22 (range 16-29) and 23 (range 22-27) mumol/mol respectively, P < 0.01]. Calcium oxalate urine saturation of stone patients was higher than that of patients with haematuria and the normal population (1.18 +/- 0.05 vs. 1.06 +/- 0.03, P < 0.03 and 0.84 +/- 0.03, P < 0.001 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

24 hour blood pressure monitoring in healthy and hypertensive children

24 Hour ambulatory blood pressure monitoring (ABPM) was performed to provide data on the normal daily blood pressure of healthy schoolchildren and on patients with hypertension. The subjects studied were 123 healthy schoolchildren with a mean (SD) age of 12.5 (1.6) years (range 9.5-14.5 years), 24 children with borderline or mild hypertension, 17 with renal hypertension and normal renal function, 10 with chronic renal failure, and six with a renal allograft. In eight children with definite renal disease a second measurement was performed after treatment modification. The monitor used for ABPM was validated with a mercury column manometer. The mean (SD) of the signed differences of the blood pressure measured by the two methods was -0.19 (1.75) mmHg for the systolic and -0.21 (2.11) mmHg for the diastolic blood pressure (n = 60). Normal values for daytime and night time blood pressure were determined for those aged 10-14 years. The mean (SD) blood pressure of the 123 children was 109 (7)/66 (8) mmHg (systolic/diastolic) for the daytime and 96 (8)/52 (7) mmHg at night time. Of the 24 children with borderline or mild hypertension 14 had a raised blood pressure on ABPM. The circadian rhythm was disturbed in three children of this group. Even children with normal daytime blood pressure had significantly higher systolic blood pressure in the night when compared with the controls. The incidence of disturbed circadian rhythm was higher in the groups with renal hypertension (4/17 in the subgroup with normal renal function, 5/16 in the group with renal failure and/or transplantation). All children undergoing a second ABPM measurement had a lower average blood pressure after treatment adjustment. ABPM measurements were reproducible and accurate. The method provided new data on the physiological circadian variation of blood pressure in healthy children. It proved to be a helpful tool in the diagnosis of hypertension, particularly in the detection of cases of disturbance of the circadian rhythm of blood pressure pattern and individual adjustment of treatment.

Determination of oxalate excretion in spot urines of healthy children by ion chromatography

Evidence for the suitability of spot urines for selective screening in children was obtained by comparing the 24-hour urinary oxalate excretion with the ratio of urinary oxalate to creatinine [mmol/mol] in spontaneously voided urine samples. Spot urines of 169 healthy children aged 1 day to 13 years were analysed in order to establish reference values for the urinary oxalate/creatinine ratio in relation to age and body surface area. Oxalate was measured by automated ion chromatography. Results showed an inverse relationship between the oxalate/creatinine ratio and age. The highest ratios, 131 +/- 57 mmol/mol (mean +/- 2 SD), were found in infants. At age two years, the ratio was 84 +/- 55, at age five years 56 +/- 35, and for children older than ten years 42 +/- 31. This finding can be explained by the gain of muscle mass and hence increased creatinine production with increasing age. Data for the urinary oxalate/creatinine ratio are presented according to body surface area for the assessment of children with abnormal growth. In 19 urine samples from nine patients with primary hyperoxaluria, the oxalate/creatinine ratio greatly exceeded (286-2022 mmol/mol) the above reference ranges. We therefore propose the determination of the oxalate/creatinine ratio in spot urines for the selective screening for hyperoxaluria in children with nephrocalcinosis or urolithiasis.

Hydrochlorothiazide treatment of children with hypercalciuria: effects and side effects

Urinary excretion of calcium and the changes in serum cholesterol fractions were investigated in 15 children with renal hypercalciuria, following 3-month hydrochlorothiazide (HCT) treatment (daily dose 1 mg/kg). Urinary calcium excretion (expressed as the ratio of calcium to creatinine) reached its lowest value after 2 weeks. It was still below the initial value at the end of the 3rd month of treatment (0.84 +/- 0.06, 0.29 +/- 0.03 and 0.6 +/- 0.09 mmol/mmol, respectively). A significant rise in the total serum cholesterol level (4.64 +/- 0.23 vs. 4.25 +/- 0.18 mmol/l before treatment, P < 0.01) and the low-density lipoprotein (LDL)-cholesterol fraction (2.6 +/- 0.24 vs. 2.31 +/- 0.31 before treatment, P < 0.01) was observed at the end of the 3rd month, while high-density lipoprotein (HDL)-cholesterol was slightly decreased. A significant elevation of the LDL/HDL ratio was also observed (from 1.76 +/- 0.17 to 2.2 +/- 0.17, P < 0.001), indicating an increase in the atherogenic cholesterol fractions. The risks and benefits of the thiazide therapy should be considered before starting long-term treatment of children with hypercalciuria and haematuria or renal stone disease.

X linked hypophosphataemia: treatment, height gain, and nephrocalcinosis

The clinical data of 18 patients with X linked hypophosphataemia were analysed retrospectively. The height data were expressed as SD scores. There was no difference in the final height of patients treated with vitamin D (or 1,25-dihydroxyvitamin D) and phosphate for at least two years (n = 12) and that of 16 hypophosphataemic family members who had never been treated. The mean final SD score (-2.07) of treated patients, however, was significantly higher than the value before treatment (-2.79), which indicated an average absolute height gain of 4-4.5 cm compared with the expected height values. Six of the treated patients developed ultrasonographically detectable nephrocalcinosis with normal renal function. The daily phosphate intake and excretion of patients with nephrocalcinosis was significantly higher than that of patients with normal renal morphology. There was no difference in the doses of vitamin D between the two groups. The average urinary calcium:creatinine ratio of the two groups was similar to and below the hypercalciuric 0.6 mmol:mmol limit. The group with nephrocalcinosis, however, had a higher incidence of hypercalciuric episodes than the group without nephrocalcinosis (12 in 130 observations compared with six in 334 observations, respectively). The benefits and risks of treatment of patients with X linked hypophosphataemia must be further evaluated. The high dose of phosphate seems to be an important factor in the development of nephrocalcinosis in this group of patients.

Evidence suggesting hyperoxaluria as a cause of nephrocalcinosis in phosphate-treated hypophosphataemic rickets

Urinary excretion of oxalate and phosphate was measured in twelve vitamin-D-treated, phosphate-supplemented patients with X-linked hypophosphataemia (XLH; four children, eight adolescents and adults) to investigate possible causative factors of nephrocalcinosis other than calcium. Oxalate excretion correlated highly with urinary phosphate excretion and with intake of phosphate supplements corrected for body surface area. Young children received the highest relative doses of phosphate (range 2.27-10.8 g/1.73 m2 daily) and their urinary oxalate excretion was very high (0.94-3.38 mmol/1.73 m2 daily). The urinary oxalate excretion of untreated adults with XLH was within normal limits. Six patients had evidence of nephrocalcinosis on ultrasound. The high urinary oxalate excretion in phosphate-supplemented XLH may be seen as a special type of enteric hyperoxaluria, in which the conditions of calcium-oxalate crystal precipitation could be reached even at normal levels of urinary calcium excretion. Urinary excretion of both calcium and oxalate should therefore be monitored during treatment in young XLH patients.

Effect of thiazide on urinary calcium excretion and hematuria in children with postglomerular hematuria

The effect of short term hydrochlorothiazide therapy on urinary calcium excretion was compared to that of low calcium and a combined low calcium and low sodium diet in 30 children with postglomerular hematuria. On basal conditions 9 children were normocalciuric, 11 had absorptive, 10 renal hypercalciuria. The effect of thiazide treatment on the haematuria was also evaluated. Thiazide revealed to be more effective in reducing calcium excretion than low calcium diet alone in all groups (p less than 0.001 in normocalciuria; p less than 0.01 in both hypercalciuric groups). Combined low calcium--low sodium diet and thiazide treatment were equally effective in reducing calcium excretion in the hypercalciuric groups. On the first 3 days of thiazide treatment a slight increase of hematuria was observed; in the following period a significant decrease in the occurrence (p less than 0.01 in both hypercalciuric groups) and degree (p less than 0.01 in absorptive; p less than 0.02 in renal hypercalciuria) of hematuria was noted. These data furnish further evidence on the relation of hypercalciuria and post-glomerular hematuria.

Studies on the urinary calcium excretion in children with hematuria of postglomerular origin: effects of the variation of dietary calcium and sodium intake

The effect of different dietary regimens and of an oral calcium (Ca) load was studied in 30 children with postglomerular hematuria, 8 of whom were renal stone formers. In addition we investigated the urinary inorganic phosphate complex composition in 12 of them, based on the principles of complex equilibria. Twenty-one of the 30 hematuric children with a urinary Ca/creatinine (Ca/cr) ratio of greater than or equal to 0.6 (mmol/mmol) were regarded as hypercalciuric. Low calcium intake normalised the ratio in 11 patients, fulfilling the definition of absorptive hypercalciuria, but not in the other 10 patients with renal hypercalciuria. Sodium restriction combined with low calcium diet induced a further significant decrease of the urinary Ca/cr ratio to a normal range in both forms of hypercalciuria (mean +/- SD: 0.325 +/- 0.112 in absorptive hypercalciuria; 0.533 +/- 235 in renal hypercalciuria). There was a significant difference in the composition of phosphate complexes between the 6 normocalciuric patients and the 6 children with renal hypercalciuria investigated. Lithogenic urinary phosphate complexes (CaHPO4, MgHPO4) were excreted by the latter group in a significantly higher amount under basal conditions. On the basis of these data sodium restriction added to low calcium diet could represent a dietary approach in preventing excessive calcium excretion in idiopathic hypercalciuria, and therefore renal stone formation.