Hypertension as related to renal function in diabetes mellitus

The relationships between blood pressure and renal function were investigated in 78 hypertensive patients with diabetes mellitus type I or II. Renal function was assessed by determining the glomerular filtration rate and the para-aminohippurate clearance in 32 and serum creatinine in 46 subjects. In the latter, the reciprocal serum creatinine, corrected for age and changing creatinine/insulin clearance ratio, was used as an estimate of glomerular filtration rate. In the 54 patients with serial determinations, the duration of follow-up averaged 10.5 years. In older patients with type II diabetes without clinical proteinuria, hypertension developed either before or after the onset of diabetes. When it appeared, renal function was only slightly reduced. During follow-up, the decline in reciprocal serum creatinine averaged 2.7% per year, a figure very similar to that found in nondiabetic patients with benign essential hypertension. It did not correlate with the blood pressure. In patients with a proteinuria greater than 2.5 g per day and histologic and/or clinical evidence of diabetic glomerulosclerosis, the severity of hypertension correlated inversely with the level of renal function. The rate of decline in function averaged 11% per year but varied widely. It was not significantly related to the blood pressure. These data suggest that different types of hypertension (essential, diabetic, and nephrogenic) may be associated with diabetes mellitus. The rate of decline in renal function is closely related to the presence or absence of clinical proteinuria but not to the level of blood pressure.