Doppler sonographic renal resistance index in healthy children

The objective of the study was to determine the values of Doppler resistance indices (RIs) in intrarenal arteries in healthy children. Color duplex Doppler sonography of intrarenal arteries was performed in 163 children and 58 adult patients, with the absence of clinical or laboratory pathologic changes of the urinary tract. All patients were classified following results of exploratory data analysis into three age groups: (a) 51 children between 2 and < 6 years of age; (b) 112 children 6-16 years of age; and (c) adults. The RIs were compared between different age groups. The mean RI +/- 1 SD values in group 1 were 0.705 +/- 0.018 (range 0.67-0.75), in group 2 0.605 +/- 0.029 (range 0.55-0.65), and in the adult group 0.604 +/- 0.035 (range 0.54-0.68). In the group of the youngest children (group 1), the RIs were significantly higher (p < 0.01) in comparison with the other group of children and the adult group. No statistically significant difference was observed between the group of children 6-16 years of age and the adult group. RI < 0.70 was noted in all children above 6 years of age; however, in younger children, RI > or = 0.70 was observed in 72.5% (37 of 51) of children. Resistance index in early childhood was considerably higher as compared with older children and the adult population: Apparently the RI value drops to adult level at approximately 6 years of age. The utilization of a threshold RI value of 0.70 for the increased renal vascular resistance in adults can also be applied to children over 6 years of age.