The nephropathy of non-insulin-dependent diabetes: predictors of outcome relative to diverse patterns of renal injury.

Abstract

Nephropathy of non-insulin-dependent diabetes mellitus (NIDDM) is the most common cause of end-stage renal failure (ESRF) in Western countries. This study investigates the clinical and histologic putative predictors of disease progression, with the final goal to identify patients at risk who may benefit from early diagnosis and intervention. It examines by repeated measurements of BP, blood glucose, serum creatinine, and urinary protein excretion rate 65 consecutive NIDDM patients with clinical, persistent proteinuria and biopsy-documented typical diabetic glomerulopathy (class I; n = 30), predominant nephroangiosclerosis (class II; n = 23), or nondiabetic type glomerulopathy (class III; n = 12), whose severity of renal tissue involvement was precisely quantified by a global histologic score. Baseline parameters and progression to renal end points, i.e., doubling of baseline serum creatinine, dialysis, or transplantation, were univariately and multivariately correlated by proportional hazards regression models. The median kidney survival time in the overall study population was 3.07 yr. Thirty-seven percent of patients reached an end point during a median (range) follow-up of 1.8 yr (0.4 to 5.7 yr). By univariate and multivariate analysis, kidney survival significantly correlated with baseline urinary protein excretion rate (P = 0.04 and P = 0.04, respectively) and renal tissue injury score (P = 0.0001 and P = 0.02, respectively), but not with the histologic classes. Patients with a urinary protein excretion rate < or = 2 g/24 h, or > 2 g/24 h with a histologic score < 7, never reached an end point. All patients with urinary protein excretion > 2 g/24 h and a histologic score > 13 progressed to ESRF over a median of 1.6 yr. No differences in other baseline parameters or in BP and diabetes control during follow-up accounted for these different outcomes. In NIDDM as well as in nondiabetic chronic renal disease, quantification of urinary protein excretion rate--independent of the pattern of underlying glomerular involvement--reliably discriminates progressors from nonprogressors and, combined with precise quantification of renal tissue injury, reliably predicts risk of ESRF. This information may be used to set guidelines for early diagnosis and appropriate intervention to reduce the number of diabetic patients who will need renal replacement therapy in years to come.