Nondiabetic kidney diseases in type 2 diabetic patients

BACKGROUND The aim of this study was to evaluate the clinical characteristics of nondiabetic nephropathy in type 2 diabetes mellitus patients and to find a clinical significance of renal biopsy and immunosuppressive treatment in such a patient. METHODS Renal biopsy results, clinical parameters, and renal outcomes were analyzed in 75 diabetic patients who underwent kidney biopsy at Chungnam National University Hospital from January 1994 to December 2010. RESULTS The three most common reasons for renal biopsy were nephrotic range proteinuria (44%), proteinuria without diabetic retinopathy (20%), and unexplained decline in renal function (20.0%). Ten patients (13.3%) had only diabetic nephropathy (Group I); 11 patients (14.7%) had diabetic nephropathy with superimposed nondiabetic nephropathy (Group II); and 54 patients (72%) had only nondiabetic nephropathy (Group III). Membranous nephropathy (23.1%), IgA nephropathy (21.5%), and acute tubulointerstitial nephritis (15.4%) were the three most common nondiabetic nephropathies. Group III had shorter duration of diabetes and lesser diabetic retinopathy than Groups I and II (P=0.008). Group II had the lowest baseline estimated glomerular filtration rate (P=0.002), with the greatest proportion of renal deterioration during follow-up (median 38.0 months, P<0.0001). The patients who were treated with intensive method showed better renal outcomes (odds ratio 4.931; P=0.01). Absence of diabetic retinopathy was associated with favorable renal outcome in intensive treatment group (odds ratio 0.114; P=0.032). CONCLUSION Renal biopsy should be recommended for type 2 diabetic patients with atypical nephropathy because a considerable number of these patients may have nondiabetic nephropathies. And intensive treatment including corticosteroid or immunosuppressants could be recommended for type 2 diabetic patients with nondiabetic nephropathy, especially if the patients do not have diabetic retinopathy.