Etiology and prognostic significance of albuminuria in diabetes.

Persistent clinical proteinuria (i.e., urinary protein excretion greater than 0.5 g/24 h) is an ominous development in a person with diabetes. It eventually leads to a decline in the glomerular filtration rate and ultimately to end-stage renal failure or premature cardiovascular mortality. Progression of renal disease appears to be related to arterial blood pressure and protein intake and is primarily independent of the metabolic state. More sensitive immunoassays for detecting low concentrations of albumin in urine have led to recognition of subclinical increases in albumin excretion rates in nonclinically proteinuric diabetic patients, a phenomenon named microalbuminuria. Studies have shown that patients with microalbuminuria have a significantly increased risk for clinical proteinuria and cardiovascular mortality. Microalbuminuria is rarely found during the first 5 yr of a patient's diabetes, suggesting that it is a sign of early glomerular damage rather than a marker for susceptibility to it. In patients with non-insulin-dependent diabetes mellitus (NIDDM), an association has been found between microalbuminuria and coronary heart disease, but this relationship needs further investigation. In patients with insulin-dependent diabetes mellitus (IDDM), this subclinical form of proteinuria is associated with poor metabolic control and, more important, with marginal elevation of blood pressure. Correction of hyperglycemia by intensified insulin treatment might arrest progression to persistent clinical proteinuria; moreover, restricted protein intake and lowering of blood pressure have been shown to reduce the albumin excretion rate.(ABSTRACT TRUNCATED AT 250 WORDS)