Mild renal dysfunction and renal vascular resistance in primary hypertension

Mild renal dysfunction (MRD) is an often overlooked but relatively common condition in patients with primary hypertension (PH), and is associated with high cardiovascular morbidity and mortality. Whether MRD is also associated with abnormalities in renal vascular resistance is currently unknown.

Two hundred ninety-one untreated patients with PH were studied. The MRD was defined as a creatinine clearance >or=60 mL/min but <90 mL/min (Cockcroft-Gault formula) or the presence of microalbuminuria. Albuminuria was measured as the albumin-to-creatinine ratio in first morning urine samples. Renal resistive index (RI) was evaluated by ultrasound Doppler of the interlobar arteries.

The prevalence of MRD in our cohort was 63%. Patients with MRD were older, had higher mean blood pressure (BP), pulse pressure, and total cholesterol, longer history of hypertension, and were more likely to be men. Renal RI was positively related to female gender, age, systolic BP, pulse pressure, total cholesterol, albuminuria, and to carotid wall thickness and cross-sectional area, whereas it was inversely related to diastolic BP and creatinine clearance. Patients with the highest renal resistance (upper quartile, >or=0.63) showed a greater prevalence of renal dysfunction (P=.0005). After adjusting for age, pulse pressure, and LDL-cholesterol, we found that the risk of MRD increased twofold (P=.04) when renal RI was >or=0.63.

A reduction in creatinine clearance and the presence of microalbuminuria are associated with increased renal vascular impedence, as well as with signs of extrarenal arterial stiffness.