The pulsatility index and the resistive index in renal arteries in patients with hypertension and chronic renal failure

Abstract

Background: The pulsatility index (PI) and the resistive index (RI) are used as pulsed-wave Doppler measurement of downstream renal artery resistance. Little information is available on their value in chronic renal failure and their correlation to parameters of renal function and haemodynamics. The aim was to compare PI and RI of renal arteries in healthy volunteers and in patients with hypertension and chronic renal failure, and furthermore to study the correlation of these indices to measurements of renal haemodynamics and function by standard methods in patients with renal failure and hypertension.

Methods: Twenty-five hypertensive patients (10 females, 15 males, mean age 52 years (24-74) with a glomerular filtration rate (GFR) less than 50 ml/min and an arterial blood pressure above 140 mmHg systolic and 95 mmHg diastolic were included in the study. Ten healthy, normotensive volunteers (4 females and 6 males, mean age 43 years (30-62)) served as controls in the Doppler examinations. Doppler examinations were performed in segmental arteries by an Acuson 128. The PI and the RI was calculated from the blood flow velocities.

Results: Both the PI and the RI were significantly higher in the patient group (P) than in the control group (C) (PI, P 1.65 (1.31-1.86), C 1.19 (0.93-1.25), P = 0.003; RI, P 0.76 (0.69-0.81), C 0.67 (0.64-0.70), P = 0.003). Both PI and RI correlated significantly with effective renal plasma flow (PI: r = -0.5, P = 0.02; RI: r = -0.5, P = 0.006), renal vascular resistance (PI: r = 0.4, P = 0.05; r = 0.5, P = 0.02), filtration fraction (PI: r = 0.6, P = 0.005; RI: r = 0.5, P = 0.01) and clearance of creatinine (PI: r = -0.6, P = 0.008; RI: r = -0.6, P = 0.006). Only RI correlated significantly to GFR (r = -0.5, P = 0.02). The indices did not correlate to serum creatinine, or mean arterial blood pressure.

Conclusion: PI and RI seems to be closely related to parameters of renal haemodynamics and clearance of creatinine in patients with chronic renal failure and hypertension.