Normoalbuminuric Diabetic Nephropathy

Recently, one of my colleagues gave an interesting talk on diabetic nephropathy without proteinuria. Traditionally, we are taught that diabetic nephropathy progresses along 5 stages: 1.Hyperfilitration, 2.Normoalubminuria, 3.Microalbuminuria, 4.Macroalbuminuria and 5.ESRD. GFR declines as patients progress from one stage to the next stage. However, according to a nice review article on diabetic nephropathy, (Jerums et al, Nature Rev Nephrol 2009), about 10-25% of patients follow 'normoalubminuric pathway' in which GFR continues to decline without worsening proteinuria. All studies excepting one quoted on this subject in the paper suffer from lack of renal biopsy to exclude other causes of low GFR such as nephrosclerosis. Caromori et al (Diabetes 2003, 52(4):1036-40) biopsied 105 type 1 diabetic patients without albuminuria and compared patients with low GFR with those with normal GFR. It was found that patients with low GFR had advanced diabetic glomerular lesions despite absence of albuminuria. These data indicate that a proportion of diabetic patients suffer decline in GFR with progressive glomerular lesions in the absence of worsening albuminuria. We have to keep this in mind in evaluation of diabetic patients in our CKD clinic.