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.