Renal biopsy in diabetic patients: Histopathological and clinical correlations

Introduction: Diabetes is the leading cause of chronic kidney disease and end-stage kidney disease worldwide. A kidney biopsy in a diabetic patient must be considered when non-diabetic renal disease is suspected, such as in the presence of a rapid decline in renal function or severe unexplained proteinuria. However, the timing and criteria of a biopsy remain controversial in these patients. We aimed to identify clinical and histological markers that could help differentiate diabetic and non-diabetic renal disease and decide if this invasive approach is needed or not. Subjects and Methods: We reviewed 30 years of biopsies from diabetic patients performed at a tertiary hospital. We collected patient demographic data, biopsy indications, histological findings, and clinical and analytical data both at the moment of the biopsy and extensive followup. Based on kidney biopsy findings, patients were categorized as isolated diabetic nephropathy, non-diabetic kidney disease, or non-diabetic kidney disease superimposed on diabetic nephropathy (diabetic kidney disease). Results and Discussion: We enrolled 92 patients, mostly with type 2 diabetes, with a mean age of 62.9 ± 13.2 years. Nearly half of them had isolated diabetic nephropathy (53.3%), and 15.2% had diabetic nephropathy superimposed on non-diabetic kidney disease, comprising a total of 63 patients (68.5%) with diabetic kidney disease. Twenty-nine patients (31.5%) were considered to have non-diabetic kidney disease. These last patients were significantly less likely to need insulin therapy (p=0.002), had more frequently an acute deterioration of renal function (p=0.01), lower albumin levels (p=0.03), and a higher prevalence of microhematuria (p=0.001). We found the latter to be an independent predictor of non-diabetic kidney disease. Further, patients with the primary diagnosis of diabetic nephropathy had higher survival than those who had nondiabetic kidney disease, contradicting published data. Conclusions: The criteria for performing a biopsy in diabetic patients still lack consensus, although the priority to identify non-diabetic kidney disease prevails. We believe the non-diabetic kidney disease predictors we describe may prove helpful for determining the need for a histological assessment in diabetic patients.