Microalbuminuria and diabetic nephropathy: Epidemiology, prognostic significance, prevention

Diabetic nephropathy is a serious complication of diabetes and the leading cause of end-stage renal disease, at least in the US, Europe and Japan. Early detection of diabetic nephropathy relies upon tests for the urinary excretion of small quantities of albumin, known as microalbuminuria. Microalbuminuria is defined as excretion of 30-300 mg of albumin/24h (or 20-200 mu g/min or 30-300 mu g/mg creatinine) in two of three collections. The pathophysiological process of microalbuminuria is not exactly understood, but it may be related to endothelial dysfunction, inflammation and abnormalities of the renin-angiotensin system. Microalbuminuria has been recognized as a predictor of progression of diabetic nephropathy but also as an independent risk factor for cardiovascular disease in both type 1 and type 2 diabetic patients. Predictors of microalbuminuria in normoalbuminuric diabetic patients include the duration of diabetes, the albumin excretion rate, blood pressure and HbA1c. Early detection of microalbuminuria allows early intervention designed to delay the onset of overt diabetic nephropathy. Therapy may include improved glycemic control, control of hypertension, dietary protein restriction and treatment with renin-angiotensin system inhibitors. Intervention studies with ACE inhibitors or angiotensin II type 1 receptor blockers (ARBs) in diabetic patients have shown that reduction of microalbuminuria can be induced. Intensified multifactorial intervention results in remission or regression of microalbuminuria and slows progression to nephropathy in diabetic patients. This review summarizes the current data about the association between albuminuria and adverse renal outcome in diabetic patients, and the possible interventions for primary and secondary prevention of this important risk marker.