Concomitance of diabetic retinopathy and proteinuria accelerates the rate of decline of kidney function in type 2 diabetic patients

OBJECTIVE - To evaluate the rate of progression of renal disease in proteinuric type 2 diabetic patients with and without retinopathy. RESEARCH DESIGN AND METHODS - Thirty-eight proteinuric type 2 diabetic patients with diabetic retinopathy and 27 without were enrolled in an observational study for the evaluation of rate of glomerular filtration rate (GFR) decline and followed up for a median period of 6 years. GFR was determined at least once per year, and blood pressure, glycated hemoglobin, and proteinuria were determined every 4 months. RESULTS - Although the two groups had comparable GFR, albuminuria, blood pressure, and HbA1c at entry of the study, the rate of decline of GFR was higher in type 2 diabetic patients with retinopathy (-6.5 ± 4.4 ml/year) than in those without (-1.8 ± 4.8 ml/year; P < 0.0001). Protein and albumin excretion rate increased significantly in patients with retinopathy, while they did not change in those without. Mean blood pressure between the two groups of patients were similar both at entry and during the follow-up, although the proportion of patients treated with at least two antihypertensive drugs was higher in patients with retinopathy. On a multiple regression analysis, only mean blood pressure and proteinuria were significant determinants of progression of renal disease in type 2 diabetic patients with retinopathy. CONCLUSIONS - The rate of progression of renal disease in proteinuric type 2 diabetic patients with retinopathy is faster than that observed in those without retinopathy. The screening for retinopathy identifies patients at high risk for rapid deterioration of kidney function.