Background: Both diabetic nephropathy (DN) and nondiabetic nephropathy (NDN) are reported to occur in patients with type 2 diabetes mellitus (DM). The precise diagnosis of the type of nephropathy has obvious clinical and prognostic implication. The aim of the study was to evaluate the histologic spectrum of nephropathy in proteinuric type 2 diabetic patients and to find the correlation between type of nephropathy and diabetic retinopathy (DR).
Methods: Twenty eight proteinuric type 2 diabetic patients were included in the study. Five patients (ADPKD 3 and chronic pyelonephritis 2) were excluded from biopsy. Percutaneous renal biopsy was carried in remaining 23 patients.
Results: There was a preponderance of male (75%) and majority of the patients were in the age group of 30-78 years. Duration of diabetes ranged between 4 months to 25 years with mean +/- SD of 10.53 +/- 7.62 years. The presenting features were nephrotic syndrome 14 (60.9%), non-nephrotic proteinuria 9 (39.1%) and impaired renal function in 19 (82.6%) patients. Renal biopsy in 23 cases revealed; isolated diabetic nephropathy 13 (56.2%), NDN7 (13.43%) and 3 (13%) patients had NDN superimposed on diabetic nephropathy. Membranous nephropathy (2), focal segmental glomerulosclerosis (2), mesangiocapillary glomerulonephritis (1) were the nondiabetic glomerular disease in our type 2 diabetic patients. Chronic pyelonephritis and ischemic interstial nephropathy was the predominant tubulointerstial lesion in this study. Diabetic retinopathy (DR) observed in 12 (75%) patients with biopsy proven DN and absent in 4 (25%) patients with DN. The distribution of renal lesions in patients with DR (n = 15) showed DN in 9 (60%), NDN 3 (20%) and remaining 3 patients had combined lesions. Renal biopsy in 8 patients without DR showed typical DN in 4 (50%) and NDN in 4 (50%) patients.
Conclusion: This study demonstrates presence of both glomerular and tubulointerstitial lesions unrelated to diabetes (NDN) in proteinuric type 2 diabetic patients. Further presence or absence of DR was a poor predictor of diabetic nephropathy because DN was noted in 50% of patients without DR and 40% of patients with DR had non-diabetic nephropathy either alone or in combination with DN.