Protein and lipid metabolism in nephrotic infants on peritoneal dialysis after nephrectomy

Influence of Age, Time, and Peritonitis on Peritoneal Transport Kinetics in Children

Objective

To evaluate peritoneal transport kinetics and its changes over time in children with and without peritonitis, and to record possible differences between children under and over 5.0 years of age.

Design

A prospective study. The patients underwent a 4hour peritoneal equilibration test (PET) comprising 2.27% dextrose with a dialysate fill volume of 1000 mL/m2 of body surface area (BSA), at baseline and after a mean of 0.8: I: 0.4 years of uninterrupted dialysis.

Patients

We investigated 28 patients on maintenance peritoneal dialysis at baseline; 10 were under 5.0 years of age. The final PET was performed in 21 patients.

Main Outcome Measures

Peritoneal equilibration rates for urea (U), creatinine (C), glucose (G), sodium, potassium, phosphate, and albumin (A) were measured. Initial and final peritoneal equilibration rates were compared. Mass transfer area coefficients (MTAC) were calculated for urea, creatinine, glucose, and albumin. Residual dialysate volume was determined.

Results

Median age at first PET was 7.6 years (range 0.3 -16.6 yr). The mean (±1 SD) 4-hour dialysate-to-plasma (DIP) ratios for U, C, and A were 0.92:1: 0.05,0.70 ± 0.12, and 0.014: I: 0.007, respectively. The mean 4-hour DIDo ratio for G was 0.32: I: 0.10. DIP and DIDo results were similar in the two age groups, and peritoneal membrane function remained stable over the study period. Mean MTAC (:1:1 SD) values were: U, 22.3: I: 4.8; C, 10.9: I: 4.1; G, 11.1: I: 3.3; and A, 0.07: I: 0.03. MTAC data were similar in the two age groups and no significant changes occurred during the study period.

Conclusions

When the volume tested in children is proportional to BSA, the solute DIP ratios seem to be age-independent. Our data provide evidence that in pediatric patients MTAC is also age-independent.

Peritoneal Dialysis in Children under 5 Years of Age

Objective

We report our experience with maintenance peritoneal dialysis (PD) in small children.

Design

This is a retrospective analysis of the patient records of all children under the age of 5 years treated with continuous peritoneal dialysis (CPD) between 1986 and 1994 in Finland.

Setting

Treatment was started and the patients were seen at the outpatient clinic at the Hospital for Children and Adolescents, University of Helsinki, every 3 months. Between these visits, they had controls at their local hospital every 2 -4 weeks.

Patients

The most common primary renal disease in these 34 patients was congenital nephrotic syndrome of the Finnish type (27 patients). Others were: congenital nephrotic syndrome (3 patients), polycystic kidney disease (1), urethral valve (1), neuroblastoma (1), and renal dysplasia (1).

Results

Mean age at onset was 1.6 years and median treatment time 9.3 months. Time spent in hospital decreased from 270 days/year in the 1980s to 150 days/year in the 1990s. Two children died (5.9%). The peritonitis rate on continuous cyclic peritoneal dialysis was 1:11.5 patient-months. Hernias were diagnosed in 29% of the patients. After 3 months half of the patients were on antihypertensive medication. Pulmonary edema was diagnosed once in 12 patients and twice in 2 patients. During the first 6 months on PD the mean height standard deviation score (hSDS) increased from -2.13 to -1.66 (p < 0.0001). The 6-month change in hSDS before initiation and 6 months after the start of CPD increased from -0.12 ± 0.68 to +0.59 ± 0.64 (p = 0.0008).

Conclusions

Our results indicate that peritoneal dialysis is feasible and safe in small children. Mortality was low and growth was good. The major challenges presented by CPD therapy were maintenance of optimal nutrition, avoidance of peritonitis, and control of volemia.

Intermittent or daily administration of 1-alpha calcidol for nephrectomised infants on peritoneal dialysis?

Secondary hyperparathyroidism and renal osteodystrophy are major problems in patients with end-stage renal failure and may result in poor growth in children on dialysis. Whether vitamin D sterols should be given intermittently or daily remains a controversial issue. We studied 16 bilaterally nephrectomised infants with congenital nephrosis of the Finnish type (median age 0.54 years), all on peritoneal dialysis. Nine of them were receiving intermittent 1-alpha calcidol therapy and seven daily 1-alpha calcidol therapy. The target serum parathyroid hormone (PTH) level was 2-3 times the upper limit of normal (ULN). There were no statistically significant differences in PTH values between the groups (1.7-times vs 0.5-times the ULN at 3 months and 3.1-times vs 3.4-times the ULN at 6 months, respectively). The required weekly doses of 1-alpha calcidol were low, and there were no significant differences between the intermittent and daily groups (0.06 microg/kg vs 0.04 microg/kg at 3 months and 0.09 microg/kg vs 0.05 microg/kg at 6 months, respectively). The infants on intermittent 1-alpha calcidol showed significant catch-up growth during dialysis after nephrectomy relative to the infants on daily 1-alpha calcidol (-1.6 SD to -0.7 SD vs -1.4 SD to -1.0 SD, respectively; P < 0.05). Our results indicate that either intermittent or daily vitamin D analogue therapy, if started early, will prevent secondary hyperparathyroidism equally well in children on peritoneal dialysis (PD), but intermittent therapy might be more favourable for growth.

Peritoneal dialysis in children: challenges for the new millennium

Advances in technology and experience accumulated over the past 2 decades have resulted in the ability to successfully provide chronic peritoneal dialysis (PD) to children of all ages and sizes. However, many important clinical issues remain, including uncertainty regarding the "optimal" dialysis dose for children, the treatment of growth retardation associated with renal insufficiency, prevention of peritonitis, and the challenge of caring for newborn infants with end-stage renal disease (ESRD). This article summarizes current knowledge in each of these 4 areas, highlighting not only the advances of the past quarter-century, but also the questions that persist as we initiate the new millennium. The outcome of children receiving PD will be markedly improved only when ongoing and future research efforts reveal the optimal solutions to these important issues.

Congenital nephrotic syndrome (NPHS1): features resulting from different mutations in Finnish patients

BACKGROUND

Congenital nephrotic syndrome (NPHS1) is a rare disease inherited as an autosomally recessive trait. The NPHS1 gene mutated in NPHS1 children has recently been identified. The gene codes for nephrin, a cell-surface protein of podocytes. Two mutations, named Fin-major and Fin-minor, have been found in over 90% of the Finnish patients. In this study, we correlated the NPHS1 gene mutations to the clinical features and renal findings in 46 Finnish NPHS1 children.

METHODS

Clinical data were collected from patient files, and kidney histology and electron microscopy samples were re-evaluated. The expression of nephrin was studied using immunohistochemistry, Western blotting, and in situ hybridization.

RESULTS

Nephrotic syndrome was detected in most patients within days after birth regardless of the genotype detected. No difference could be found in neonatal, renal, cardiac, or neurological features in patients with different mutations. Nephrin was not expressed in kidneys with Fin-major or Fin-minor mutations, while another slit diaphragm-associated protein, ZO-1, stained normally. In electron microscopy, podocyte fusion and podocyte filtration slits of various sizes were detected. The slit diaphragms, however, were missing. In contrast to this, a nephrotic infant with Fin-major/R743C genotype expressed nephrin in kidney had normal slit diaphragms and responded to therapy with an angiotensin-converting enzyme inhibitor and indomethacin.

CONCLUSIONS

The most common NPHS1 gene mutations, Fin-major and Fin-minor, both lead to an absence of nephrin and podocyte slit diaphragms, as well as a clinically severe form of NPHS1, the Finnish type of congenital nephrotic syndrome.

Adequacy of dialysis with tidal and continuous cycling peritoneal dialysis in children

BACKGROUND

Today the major outcome measure for peritoneal dialysis is adequacy. We seek the optimal dialysis modality and prescription for each patient. Tidal dialysis (TPD) was introduced in 1990 to increase efficacy. However, studies with TPD have been inconsistent, and results in small children are lacking.

METHODS

Nine patients under and eight patients over 5 years of age who were undergoing or starting maintenance peritoneal dialysis (PD) were studied. Patients were dialysed with TPD and with continuous cycling PD (CCPD), each for 6 months. To optimize TPD and CCPD modalities, we recorded urea K(t)/V, creatinine clearance (CrCl), peritoneal membrane capacity, clinical examination, biochemical values and nutrition.

RESULTS

The mean nightly dialysate flow rate was significantly higher with TPD than with CCPD (46.4+/-3.7 vs 32.7+/-4.6 ml/kg/h, P:<0.001). Mean total CrCl at the baseline was significantly higher with TPD (79. 3+/-18.5 vs 72.5+/-16.0, P:=0.02), but urea K(t)/V was similar (3. 5+/-0.5 vs 3.3+/-0.4, P:=0.28). Urea K(t)/V and CrCl were higher during TPD in patients with high peritoneal membrane permeability, but similar in patients with high-average membrane permeability. Urea K:(t)/V and CrCl in CCPD and TPD did not differ significantly in the age groups. Nor did the incidence of hypertension differ in CCPD and TPD, despite a significantly lower glucose concentration during TPD.

CONCLUSIONS

Both TPD and CCPD provide adequate dialysis for paediatric patients under and over 5 years of age. Because of higher costs, we recommend TPD only for paediatric patients with high membrane permeability and reduced ultrafiltration or with mechanical outflow problems or outflow pain.

Management of congenital nephrotic syndrome of the Finnish type

Congenital nephrotic syndrome of the Finnish type (CNF) is a rare autosomal recessively inherited disease characterised by intrauterine onset of massive urinary loss of proteins, 90% of which is albumin. The CNF gene has been localised to the long arm of chromosome 19, but the pathogenesis remains unclear. Historically, all CNF patients died, usually within the first 6 months of life. Today, a normal life can be achieved for a child with CNF by correcting the protein deficiency and normalising nutrition. This is accomplished by early intravenous albumin supplementation, nutritional support, aggressive treatment of complications and early renal transplantation, after bilateral nephrectomy and peritoneal dialysis. In the present article current treatment strategies are reviewed, and our own experience with 43 CNF patients during the last 10 years is presented.

Exclusion of eight genes as mutated loci in congenital nephrotic syndrome of the Finnish type

The congenital nephrotic syndrome of the Finnish type (CNF) is an autosomal recessive disease characterized by massive proteinuria already at birth. The gene locus defective in CNF was searched for using polymorphic markers of candidate genes coding for components of the basement membrane (BM). The linkage analyses in 17 Finnish CNF families demonstrated exclusion of obligatory recombination events between the disease and eight genes coding for BM components. The genes coding for the alpha 1(IV), alpha 2(IV), alpha 3(IV) and alpha 4(IV) chain of type IV collagen, the B1e, B2e and B2t chains of laminin, as well as the BM heparan sulfate proteoglycan core protein were all excluded in this Finnish family material. Since the defect is not in any of the genes coding for major components of BM, the identification of the gene defect will most probably reveal a new gene important for the development and function of the glomerular basement membrane.

Post-transplantation nephrosis in congenital nephrotic syndrome of the Finnish type

Congenital nephrotic syndrome of the Finnish type (CNF) is an autosomal recessively inherited disease manifesting as massive proteinuria, edema and ascites in the neonatal period. The disease is believed to be limited to the kidneys and recurrences after renal transplantation have not been reported. At our center 29 transplantations have been performed on 28 CNF patients. One to 33 months after transplantation, seven grafts (24%) of six patients have developed a steroid-resistant nephrotic syndrome. The clinical data and renal histology of these patients were analyzed in order to elucidate the cause of the proteinuria. At the onset of six of the seven episodes of nephrosis, the patient had evidence of a preceding CMV- or EBV-infection and the remaining patient had sinusitis. Upon light and electron microscopy examination, endothelial swelling of the glomerular capillaries resembling transplant glomerulopathy (TG) was seen, but unlike TG, the glomerular basement membranes were normal. The response of proteinuria to steroid or cyclophosphamide therapy was poor, with total remission in only two patients and partial remission in one patient, all treated with methylprednisolone and cyclophosphamide immediately after the diagnosis. Four grafts have been lost. Our data show that CNF patients have an increased tendency for post-transplantation nephrosis.