Intrarenal Doppler: characteristics of aging kidneys

The normal range of Doppler findings in native kidneys has not been studied extensively. This study correlates changes in Doppler resistive index (RI) with age in patients without renal risk factors or renal disease. Young and old patients demonstrated the highest RI values (age < 1, mean RI = 0.73; age > 59, RI = 0.68), and patients in the 20-39 year age group showed the lowest values (RI = 0.59). The mean RI for all ages was 0.63. The cause of this variability is unknown. We suggest that age-related changes in Doppler values should be considered in the interpretation of renal Doppler measurements.