Increased blood pressure in diabetes: essential hypertension or diabetic nephropathy?

This study was performed to evaluate whether it is possible to distinguish between diabetics with essential hypertension and diabetics with elevated blood pressure due to diabetic nephropathy. We investigated 46 young diabetics, 21 having incipient nephropathy defined as urinary albumin excretion (UAE) persistently above 15 micrograms/min and total urinary protein less than 0.5 g per 24 h, and 25 patients having overt nephropathy with total protein excretion equal to or above 0.5 g per 24 h. Twenty-three patients with essential hypertension were also studied as well as 24 healthy controls. Only males and females between the age of 25 years and 40 years were included. We found a positive correlation between UAE and blood pressure (BP) but a considerable overlap in BP and UAE values between diabetics and patients with essential hypertension. However, plotting urinary albumin excretion against BP, diabetics and non-diabetics with essential hypertension could be nearly totally separated. Comparison at a similar blood pressure level, for example, mean arterial blood pressure of 125 mmHg, shows that diabetics have UAE 100 times higher than non-diabetic essential hypertensives. Conversely, UAE of 100 micrograms/min would imply that mean arterial blood pressure is about 70 mmHg higher in the non-diabetic essential hypertensives than in the diabetics. Five diabetics with normal UAE and elevated blood pressure higher or equal to 160/95 mmHg were clearly within the area of the essential hypertensive patients. Our observations indicate that it seems possible to distinguish diabetic patients with essential hypertension from diabetics with elevated blood pressure due to early or advanced nephropathy.