Histological predictors for renal prognosis in diabetic nephropathy in diabetes mellitus type 2 patients with overt proteinuria

Aim: Although several clinical risk factors for end-stage renal disease in diabetic nephropathy are known, the pathological findings that may help predict renal prognosis have not yet been defined. Methods: We enrolled 69 diabetes mellitus type 2 patients with overt proteinuria and biopsy-confirmed diabetic nephropathy with mesangial expansion, and retrospectively examined the association of histological and clinical findings with renal outcome. The median follow-up duration was 52 months. Histological scoring was made according to that of Tervaert et al. Patients were divided into four groups according to glomerular classification (class 2a, mild mesangial expansion, n = 11; class 2b, severe mesangial expansion without nodular sclerosis, n = 15; class 3, nodular sclerosis, n = 36; class 4, global glomerulosclerosis observed in more than 50% of glomeruli, n = 7). Interstitial and vascular lesions were scored for each patient. A renal event was defined as a condition requiring the initiation of chronic dialysis or doubling of the serum creatinine level. Results: Cox proportional hazard analysis showed that the glomerular classes were not significant variables, while interstitial fibrosis, tubular atrophy and interstitial inflammation were independent variables associated with renal end-point (HR: 3.36 (95% confidence interval: 1.21-9.32), 4.74 (1.26-17.91)). There were no significant differences in the renal survival rates between the glomerular classes 2a and 2b combined group and the glomerular class 3 group (P = 0.17, log-rank test). Conclusion: Interstitial lesions but not glomerular lesions were a significant predictor for renal prognosis in diabetic nephropathy in type 2 diabetes patients with overt proteinuria.