The pulsatility index and the resistive index in renal arteries. Associations with long-term progression in chronic renal failure.
BACKGROUND: The pulsatility index (PI) and the resistive index (RI) are used as pulsed-wave Doppler measurements of downstream renal artery resistance. PI and RI have been found to correlate with renal vascular resistance, filtration fraction and effective renal plasma flow in chronic renal failure. The aim of the present study was to evaluate the potential relationship between these indices and the rate of decline in renal function, as reflected by changes in different parameters of renal function in patients with chronic renal failure. METHODS: Twenty-one patients (8 females; 13 males, mean age 58 years (36-75)) with chronic renal failure were enrolled in the study. Doppler examinations were performed in the segmental arteries by an Acuson 128XP. The PI and the RI was calculated from the blood flow velocities. Parameters of renal function were measured every 3 1/2 months, and all patients were followed for 18-21 months. Progression of renal dysfunction was estimated by linear regression of parameters of renal function versus time. RESULTS: In a multiple regression analysis both PI and RI correlated significantly to the rate of decline in reciprocal serum creatinine (PI: r = -0.48, P = 0.03; RI: r = -0.52, P = 0.02). Furthermore, when separating the patients in two groups by the median RI value, there was a significant difference between the groups in rate of decline in reciprocal serum creatinine (P = 0.02). For PI this distinction was also present (P = 0.04). CONCLUSION: PI and RI correlated to the severity of the renal disease, as reflected by the rate of decline in reciprocal serum creatinine during antihypertensive treatment. The median RI or PI value could separate the patients into groups one of slow and another of fast progression.