Eileen N. Ellis

Structural-functional relationships in diabetic nephropathy.

Renal biopsies in 45 patients with insulin-dependent diabetes mellitus (IDDM) were examined by semiquantitative light microscopy and quantitative electron microscopic stereologic morphometry. In these 14 males and 31 females, aged 13-52 yr, who had had IDDM for 2.5-29 yr there was no strong relationship between either glomerular basement membrane (GBM) thickness or mesangial expansion and duration of IDDM. There was only a weak relationship between the thickness of the GBM and expansion of the mesangium. Thus, GBM thickening and mesangial expansion in IDDM occur at rates that often differ from one another and that vary greatly among patients. The clinical manifestations of diabetic nephropathy, albuminuria, hypertension, and decreased glomerular filtration rate related poorly or not at all to GBM thickening. In contrast, all light and electron microscopic measures of mesangial expansion were strongly related to the clinical manifestations of diabetic nephropathy, although in the absence of these clinical findings, it was not possible to predict the severity of any of the diabetic glomerular lesions. Mesangial expansion had strong inverse correlations with capillary filtering surface area density. It is hypothesized that mesangial expansion could lead to glomerular functional deterioration in IDDM by restricting the glomerular capillary vasculature and its filtering surface. However, capillary closure, glomerular sclerosis, and interstitial fibrosis could also contribute to the clinical manifestations of this disorder.

Circulating Factor Associated with Increased Glomerular Permeability to Albumin in Recurrent Focal Segmental Glomerulosclerosis

BACKGROUND Heavy proteinuria and progressive renal injury recur after transplantation in up to 40 percent of patients with renal failure caused by idiopathic focal segmental glomerulosclerosis. A circulating factor may be responsible for this recurrence. METHODS To determine whether patients with focal segmental glomerulosclerosis have a circulating factor capable of causing glomerular injury, we tested serum samples from 100 patients with the disorder in an in vitro assay of glomerular permeability to albumin. Of the 56 patients who had undergone renal transplantation, 33 had recurrences. Sixty-four patients, many of whom had undergone transplantation, were being treated with dialysis. Thirty-one patients with other renal diseases and nine normal subjects were also studied. RESULTS The 33 patients with recurrent focal segmental glomerulosclerosis after transplantation had a higher mean (+/-SE) value for permeability to albumin (0.47+/-0.06) than the normal subjects (0.06+/-0.07) or the patients who did not have recurrences (0.14+/-0.06). After plasmapheresis in six patients with recurrences, the permeability was reduced (from 0.79+/-0.06 to 0.10+/-0.05, P = 0.008), and proteinuria was significantly decreased. Patients with corticosteroid-sensitive nephrotic syndrome or with membranous nephropathy after transplantation had low levels of serum activity. The circulating factor bound to protein A and hydrophobic-interaction columns and had an apparent molecular mass of about 50 kd. CONCLUSIONS A circulating factor found in some patients with focal segmental glomerulosclerosis is associated with recurrent disease after renal transplantation and may be responsible for initiating the renal injury.

Cytomegalovirus infections following renal transplantation – effects of antiviral prophylaxis: a report of the North American Pediatric Renal Transplant Cooperative Study

Post-transplant cytomegalovirus (CMV) infections are a source of significant morbidity. However, the extent of the problem and the benefits of various antiviral prophylactic therapies remain incompletely understood. The North American Pediatric Renal Transplant Cooperative Study registry was screened to identify patients hospitalized for CMV infections during the 1st post-renal transplant year between 1987 and 1993. Using a control group of transplant recipients, we performed a retrospective analysis of risk factors for CMV disease among these hospitalized patients and studied the effects of various viral prophylactic strategies on CMV risk, clinical manifestations, and outcome. We identified 142 patients hospitalized with CMV infections, the majority of which included major organ involvement. A CMV-positive kidney donor was the most significant risk factor for hospitalization [odds ratio (OR) = 5.2, P<0.0001] irrespective of recipient age or CMV immune status. As opposed to antiviral agents (acyclovir, ganciclovir) or pooled IgG, prophylaxis with enriched anti-CMV IgG significantly reduced the risk of CMV hospitalization (OR = 0.31, P = 0.03). The prophylactic use of antiviral agents was associated with a decreased risk of major organ involvement during the CMV infection (OR = 0.34, P<0.005). Among the patients with CMV, the 3-year graft survival was significantly better for those who received any form of prophylaxis compared with those who received none (88% vs. 52%, P<0.001). Our findings suggest a role for combined CMV-enriched IgG and antiviral agent prophylaxis for post-transplant CMV disease. Such an approach could diminish the incidence and severity of CMV infection and appears to have an independent favorable effect on graft outcome.

Renal structural-functional relationships in early diabetes mellitus

Abstract.  To define the earliest renal morphological changes in patients with type I diabetes, we studied renal function and morphometric analysis of renal biopsies in 59 patients with diabetes for 5 – 12 years and normal blood pressure, normal creatinine clearance (CCr), and negative dipstick urinary protein. Arteriolar hyalinization and intimal fibrous thickening were noted in 43%. Glomerular basement membrane thickness and fractional mesangial volume were increased in 51% and 56%, respectively. The pre-pubertal and post-pubertal years of diabetes were associated with similar degrees of renal structural changes, but during the pre-pubertal years normal urinary albumin excretion (UAE) was seen. Principal factor analysis of morphometric structural parameters yielded four clusters of variables: “glomerular size” correlated with patient age, CCr, and UAE; “peripheral capillary decrease” correlated with glycosylated hemoglobin, diastolic blood pressure, glomerular filtration rate, and UAE; “mesangial increase” correlated with UAE; and “interstitial scarring” correlated with diastolic blood pressure. This study provides unique documentation of renal structural abnormalities which precede clinically evident renal functional abnormalities and documents that these early structural abnormalities are present in the pre-pubertal years of diabetes as well as postpuberty, and are associated with each other in constellations that correspond to postulated mechanisms in diabetic nephropathy.

Relationship of renal size to nephropathy in Type 1 (insulin-dependent) diabetes

SummaryThirty-five patients with Type 1 (insulin-dependent) diabetes mellitus and 90 normal subjects had renal size (renal area index) determined by X-ray and also had examination of renal biopsies by light and electron microscopy. Renal area index of 206±32 cm2/1.73 m2 (mean±SD) in the Type 1 diabetic patients exceeded that in the normal subjects (180±25 cm2/1.73 m2, p<0.001). In the diabetic patients, the renal area index correlated with creatinine clearance (r=+0.43, p<0.05), but did not correlate with urinary albumin excretion, or the electron microscopic measurements of percentage total mesangium and glomerular basement membrane width. In diabetic patients with clinical nephropathy or severe glomerulopathy on biopsy, the kidneys may remain large. Thus, renal size does not indicate the severity of diabetic renal lesions on biopsy.

Urinary Excretion of N-Acetyl-Beta-D-Glucosaminidase in Children with Type I Diabetes Mellitus

N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme, has been shown to be increased in the urine of patients with various glomerulonephritides, tubulointerestitial diseases, renal allograft rejection, toxic renal injury, and diabetes mellitus. Although it has been suggested that urinary NAG may reflect blood glucose control, no studies have correlated this with other measures of metabolic control. Thirty-four children from a diabetic summer camp were found to have urinary NAG to creatinine ratios significantly above those of normal controls of similar age (5.22 ± 1.19 versus 1.51 ± 0.17 U). Urinary NAG was found to positively correlate with an arbitrary control index (r =0.82; P < 0.05) and in seven patients with hemoglobin A1c (r =0.70; P < 0.001). In a closely followed group of 40 clinic patients, urinary NAG to creatinine ratio was again found to be significantly increased over normal controls (7.55 ± 0.70 versus 1.51 ± 0.17 U; P < 0.05). Again, urinary NAG was positively correlated with HbA1c (r =0.62; P < 0.001) and urinary albumin to creatinine ratio (r =0.47; P < 0.01). In neither group was there a correlation with UNAG:UCr and duration of disease. Thus, these data suggest that urinary NAG to creatinine ratio appears to be a reflection of blood sugar control.

UGT1A9, UGT2B7, and MRP2 genotypes can predict mycophenolic acid pharmacokinetic variability in pediatric kidney transplant recipients.

Background: Mycophenolic acid (MPA) exposure in pediatric patients with kidney transplant receiving body surface area (BSA)–based dosing exhibits large variability. Several genetic variants in glucuronosyltransferases (UGTs) and of multidrug resistance–associated protein 2 (MRP2) have independently been suggested to predict MPA exposure in adult patients with varying results. Here, the combined contribution of these genetic variants to MPA pharmacokinetic variability was investigated in pediatric renal transplant recipients who were on mycophenolic mofetil maintenance therapy. Methods: MPA and MPA-glucuronide concentrations from 32 patients were quantified by high-performance liquid chromatography. MPA exposure (AUC) was estimated using a 4-point abbreviated sampling strategy (predose/trough and 20 minutes, 1 hour, and 3 hours after dose) using a validated pediatric Bayesian estimator. Genotyping was performed for all of the following single nucleotide polymorphisms (SNPs): UGT1A8 830G>A(*3), UGT1A9 98T>C(*3), UGT1A9-440C>T, UGT1A9-2152C>T, UGT1A9-275T>A, UGT2B7-900A>G, and MRP2-24T>C. Results: Recipients heterozygous for MRP2-24T>C who also had UGT1A9-440C>T or UGT2B7-900A>G (n = 4), and MRP2-24T>C-negative recipients having both UGT1A9-440C>T and UGT2B7-900A>G (n = 5) showed a 2.2 and 1.7 times higher dose-dependent and BSA-normalized MPA-AUC compared with carriers of no or only 1 UGT-SNP (P < 0.001 and P = 0.01, respectively) (n = 7). Dose-dependent and BSA-normalized predose MPA concentrations were 3.0 and 2.4 times higher, respectively (P < 0.001). Interindividual variability in peak concentrations could be explained by the presence of the UGT1A9-440C>T genotype (P < 0.05). Conclusion: Our preliminary study demonstrates that combined UGT1A9-440C>T, UGT2B7-900A>G, and MRP2-24T>C polymorphisms can be important predictors of interindividual variability in MPA exposure in the pediatric population.

Use of pump-assisted hemofiltration in children with acute renal failure

Abstract. In critically ill children, acute renal failure (ARF) is associated with a high mortality. To assess the outcome and complications of pump-assisted hemofiltration (PAHF) using a standard volumetric pump to regulate blood flow, we retrospectively reviewed our experience in 52 patients with ARF treated with PAHF from 1989 to 1995. These patients ranged in age from <1 month to 19 years and in weight from 2 to 125 kg. The most common underlying diagnoses were congenital heart disease and infection. The duration of PAHF averaged 9±8 days (range 24 h to 43 days). Hemodiafiltration for solute control was required in 40 patients. Total fluid intake while on PAHF was 136±95 ml/kg per day, while urine output and ultrafiltration averaged 15±24 ml/kg per day and 89±58 ml/kg per day, respectively. Management of laboratory abnormalities was efficient with only 4 patients requiring 1 or 2 additional treatments of hemodialysis for control of uremia. Complications included hyponatremia in 13 patients, hypokalemia in 14 patients, hypovolemia in 8 patients, hyperglycemia in 6 patients, and bleeding in 9 patients. No complications specifically related to use of the volumetric infusion pump for PAHF were noted. PAHF using a volumetric infusion pump for blood flow regulation in critically ill children with ARF is a practical and efficient therapy.

Spectrum of disease associated with anti-neutrophil cytoplasmic autoantibodies in pediatric patients.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) are usually determined during the diagnostic evaluation of systemic vasculitis and glomerulonephritis syndromes in adult patients, but few pediatric patients with ANCA have been reported. We describe five pediatric patients with ANCA and glomerulonephritis, with and without upper or lower respiratory tract disease. We compared these five patients and six previously described patients to affected adults; the spectrum of ANCA-associated disease appears to be similar in adults and children, but a female predominance may exist in the pediatric patients. Pediatric patients often had end-stage renal disease within 1 year after onset. We conclude that ANCA is a useful diagnostic tool in both pediatric and adult patients with systemic vasculitis and glomerulonephritis.

UGT Genotype May Contribute to Adverse Events Following Medication With Mycophenolate Mofetil in Pediatric Kidney Transplant Recipients

Leukopenia and diarrhea are the predominant adverse events associated with mycophenolate mofetil (MMF), leading to dose reduction or discontinuation in children. Polymorphisms of the drugs main metabolizing enzyme, uridine diphosphate–glucuronosyl transferase (UGT), confer alteration in drug exposure. We studied the incidence of these polymorphisms in pediatric kidney transplant recipients experiencing MMF‐associated leukopenia and diarrhea. UGT genotypes of 16 affected children who recovered after MMF dose reduction or discontinuation were compared with those of 22 children who tolerated the drug at standard doses. DNA was extracted and sequenced using standard procedures to detect polymorphisms associated with increased (e.g., UGT1A9 −331T>C) or decreased drug exposure. All three patients who were homozygous for UGT1A9 −331T>C developed leukopenia, and heterozygotes also had significantly more toxicity (P = 0.04). A weaker association (P = 0.08) existed in UGT2B7 −900G>A carriers. Our data implicate UGT polymorphisms associated with altered drug exposure as potential predictors of MMF adverse events.