Background: The diagnosis of diabetic nephropathy (DN) is always based on clinical grounds. However, the necessity for renal biopsy of type 2 diabetes mellitus (DM) patients with renal disease to establish the diagnosis remains unclear.
Methods: We retrospectively studied 50 type 2 diabetic patients performed with renal biopsy between December 2002 and December 2006. Based on renal pathology, patients were divided into group I: DN alone, group II: non-diabetic renal disease (NDRD) superimposed on DN and group III: isolated NDRD. Factors like DM > 10 years, retinopathy, previous minimal proteinuria without sudden heavy proteinuria, no glomerular haematuria and non-small-sized kidney were collected to evaluate their sensitivity, specificity, positive predictive value and negative predictive value for prediction of DN or NDRD in type 2 diabetic patients.
Results: Group I consisted of 24 patients, group II 15 patients and group III 11 patients. Acute interstitial nephritis was the most prevalent second renal disease in our study. Sensitivity and specificity for group I was poor in five features except high sensitivity in no sudden heavy proteinuria (83.3%) and non-small-sized kidney (95.8%). Comparable retinopathy, sudden heavy proteinuria and haematuria (p > 0.05) was noted between the three groups. Significant biopsy indicators included higher serum albumin, lower urinary daily protein excretion and lower 24-h creatinine clearance (C(Cr)) rate (p < 0.05).
Conclusion: Our study demonstrated that DM > 10 years and retinopathy did not exclude NDRD in type 2 DM patients, and need for renal biopsy. Higher serum albumin, lower urinary daily protein and 24-h C(Cr) were indicative for biopsy to exclude NDRD.