Relation between proteinuria and morphology in IgA nephropathy

The Oxford classification of IgA nephropathy: rationale, clinicopathological correlations, and classification

IgA nephropathy is the most common glomerular disease worldwide, yet there is no international consensus for its pathological or clinical classification. Here a new classification for IgA nephropathy is presented by an international consensus working group. The goal of this new system was to identify specific pathological features that more accurately predict risk of progression of renal disease in IgA nephropathy, thus enabling both clinicians and pathologists to improve individual patient prognostication. In a retrospective analysis, sequential clinical data were obtained on 265 adults and children with IgA nephropathy who were followed for a median of 5 years. Renal biopsies from all patients were scored by pathologists blinded to the clinical data for pathological variables identified as reproducible by an iterative process. Four of these variables: (1) the mesangial hypercellularity score, (2) segmental glomerulosclerosis, (3) endocapillary hypercellularity, and (4) tubular atrophy/interstitial fibrosis were subsequently shown to have independent value in predicting renal outcome. These specific pathological features withstood rigorous statistical analysis even after taking into account all clinical indicators available at the time of biopsy as well as during follow-up. The features have prognostic significance and we recommended they be taken into account for predicting outcome independent of the clinical features both at the time of presentation and during follow-up. The value of crescents was not addressed due to their low prevalence in the enrolled cohort.

Is the urinary protein excretion pattern compatible with renal morphological findings in renal amyloidosis?

The aims of this study are to compare urinary protein excretion pattern with renal morphological findings and to find out whether urinary protein excretion pattern is a prognostic indicator of renal amyloidosis. Fifteen children with renal amyloidosis secondary to familial Mediterranean fever were included in the study. The patients were classified into three groups according to the degree of tubulointerstitial injury in renal biopsy (group 1, <25%; group 2, 25-50%; and group 3, >50%). In all patients, urinary protein electrophoresis were performed. Levels of urinary beta(2)-microglobulin, retinol binding protein, and beta.N-acetyl-D glucosaminidase were measured as markers for tubular injury, and urinary excretions of protein and albumin and plasma albumin levels were measured as markers of glomerular injury. While urinary excretions of protein and albumin and plasma albumin levels were not different between groups, higher urinary beta(2-)microglobulin and retinol binding protein values and lower creatinine clearance values were found in group 3 than in groups 1 and 2 (p < 0.05). We concluded that analysis of urinary protein excretion pattern is a non-invasive and reliable method to detect the degree of tubulointerstitial injury as the most important prognostic factor in renal amyloidosis and may be used to determine the changes during the follow-up period of the patients.

ACEI/ATRA therapy decreases proteinuria by improving glomerular permselectivity in IgA nephritis

BACKGROUND

It has been postulated that angiotensin-converting enzyme inhibitor/angiotensin receptor antagonist (ACEI/ATRA) may decrease proteinuria in patients with glomerulonephritis by its action on the glomerular basement membrane. We therefore studied the relationship between the response of patients with IgA nephritis (IgAN) to ACEI/ATRA therapy by decreasing proteinuria and its effect on the selectivity index (SI) in these patients.

METHODS

Forty-one patients with biopsy-proven IgAN entered a control trial, with 21 in the treatment group and 20 in the control group. The entry criteria included proteinuria of 1 g or more and/or renal impairment. Patients in the treatment group received ACEI/ATRA or both with three monthly increases in dosage. In the control group, hypertension was treated with atenolol, hydrallazine, or methyldopa. The following tests were performed at three monthly intervals: serum creatinine, total urinary protein, SI, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and low molecular weight (LMW) proteinuria.

RESULTS

After a mean duration of therapy of 13 +/- 5 months, in the treatment group, there was no significant change in serum creatinine, proteinuria, or SI, but in the control group, serum creatinine deteriorated from 1.8 +/- 0.8 to 2.3 +/- 1.1 mg/dL (P < 0.05). Among the 21 patients in the treatment group, 10 responded to ACEI/ATRA therapy determined as a decrease in proteinuria by 30% (responders), and the other 11 did not respond (nonresponders). Among the responders, SI improved from a mean of 0.26 +/- 0.07 to 0.18 +/- 0. 07 (P < 0.001), indicating a tendency toward selective proteinuria. This was associated with an improvement in serum creatinine from mean 1.7 +/- 0.6 to 1.5 +/- 0.6 mg/dL (P < 0.02) and a decrease in proteinuria from a mean of 2.3 +/- 1.1 to 0.7 +/- 0.5 g/day (P < 0. 001). After treatment, proteinuria in the treatment group (1.8 +/- 1. 6 g/day) was significantly less than in the control group (2.9 +/- 1. 8 g/day, P < 0.05). The post-treatment SI in the responder group (0. 18 +/- 0.07) was better than that of the nonresponder group (0.33 +/- 0.11, P < 0.002). Eight out of 21 patients in the treatment group who had documented renal impairment had improved renal function compared with two in the control group (chi2 = 4.4, P < 0. 05). Of the eight patients in the treatment group who improved their renal function, three normalized their renal function compared with one from the control group.

CONCLUSION

Our data suggest that ACEI/ATRA therapy may be beneficial in patients with IgAN with renal impairment and nonselective proteinuria, as such patients may respond to therapy with improvement in protein selectivity, decrease in proteinuria, and improvement in renal function. ACEI/ATRA therapy probably modifies pore size distribution by reducing the radius of large unselective pores, causing the shunt pathway to become less pronounced, resulting in less leakage of protein into the urine.