Standardizing resistive indices in healthy pediatric transplant recipients of adult-sized kidneys.

Small pediatric recipients of an adult-sized kidney have insufficient renal blood flow early after transplantation, with secondary chronic hypoperfusion and irreversible histological damage of the tubulo-interstitial compartment. It is unknown whether this is reflected by renal resistive indices. We measured renal graft resistive indices and volumes of 47 healthy pediatric kidney transplant recipients of an adult-sized kidney in a prospective study for six months post-transplant. A total of 205 measurements were performed. The smallest recipients (BSA <or=0.75 m(2)) had higher resistive indices compared to recipients with a BSA between 0.75 and 1.5 m(2) (p < 0.0001) and to recipients with a BSA >or= 1.5 m(2) (p < 0.0001). Resistive indices increased during the first six months in the smallest recipients (p = 0.02), but not in the two larger recipient groups (BSA 0.75-1.5 m(2) and >or=1.5 m(2)). All three BSA groups showed a reduction in renal volume after transplantation, with the greatest reduction occurring in the smallest recipients. In conclusion, renal transplant resistive indices reflect pediatric recipient BSA dependency. The higher resistance to intra-renal vascular flow and significant decrease in renal volume in the smallest group likely reflect accommodation of the size discrepant transplanted adult-sized kidney to the smaller pediatric recipient vasculature with associated lower renal artery flow.