Background: Microalbuminuria is widely accepted as the first clinical sign of diabetic nephropathy. However, normoalbuminuric type 2 diabetic patients who have renal insufficiency (RI), i.e. low estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2), exist. We explored the prevalence of such patients and associated clinical factors.
Methods: We investigated the distribution of patients when stratified by albuminuria stages and chronic kidney disease (CKD) stages in a large-scale population of Japanese type 2 diabetic patients (N = 3297), and the common and independent factors for albuminuria and low eGFR.
Results: The proportion of subjects with low eGFR was 15.3% (506/3297), which was 11.4% among those with normoalbuminuria (NA) (262/2298), 14.9% among those with microalbuminuria (105/705) and 47.3% among those with macroalbuminuria (139/294). There were 262 patients with NA and low eGFR, and 63.4% of them had neither diabetic retinopathy nor neuropathy. They were older and included a higher proportion of women and patients with hypertension, hyperlipidaemia and cardiovascular disease (CVD), and fewer smokers compared with those with NA and preserved eGFR. Multiple logistic regression analysis revealed that factors commonly associated with RI and albuminuria were hypertension, CVD and proliferative retinopathy. Factors independently associated with RI were age, duration of diabetes, A1C (negative), hyperlipidaemia, smoking (negative) and macroalbuminuria, whereas those associated with albuminuria were male sex, BMI, A1C, simple retinopathy and RI.
Conclusions: A significant proportion of type 2 diabetic patients have normoalbuminuric RI. Renal disease in type 2 diabetes could be heterogeneous, implying the possibility of involvement of renal atherosclerosis and lipid toxicity.