Hypertension and microalbuminuria as predictors of diabetic nephropathy

Renal disease affects approximately 35% of insulin-dependent diabetic patients with a maximal incidence of approximately 25 per 1 000 patient-years after a duration of about 16 years, declining thereafter to less than 7 per 1 000 patient-years after 35 years of diabetes and suggesting that only a particular subset of patients is at risk. The renal disease is characterized by a triad comprising increased albuminuria, arterial pressure and volume fraction of mesangium and leads to a decline in the glomerular filtration rate and ultimately to end stage renal failure or premature cardiovascular mortality. Individuals at risk can be detected before the development of persistent proteinuria by screening for microalbuminuria which has proven predictive of clinical nephropathy in about 80% of cases. Microalbuminuria is accompanied by subclinical increases in arterial blood pressure and plasma lipids and may be associated with increased glomerular filtration rate. It is not usually apparent within the first five years of diagnosis of diabetes. Microalbuminuria thus appears to be a marker for the presence of early renal disease rather than a predictor of susceptibility to it and its many associations indicate it to be a marker of systemic rather than merely renal disease. Recent evidence suggests that diabetic renal disease may be linked to a familial, possibly genetically determined predisposition to arterial hypertension or to some factor closely related to the risk of hypertension. Such a predisposition may help to explain why clinical renal disease occurs in only a subset of diabetic patients.