Duplex Doppler analysis of interlobular arteries in transplanted kidneys

The aim of our study was to analyze changes in spectral Doppler waveforms between interlobar and interlobular arteries in renal transplants and to determine whether sampling location at interlobular level can be suitable for intrarenal resistive index (RI) measurements. Paired series of spectral tracings from interlobar arteries and respective interlobular branches were obtained in 62 consecutive renal transplants at 6.5-MHz Doppler frequency. The values of peak systolic velocity (PSV), end diastolic velocity (EDV) and RI were significantly (P < 0.01) reduced when calculated at interlobular level. In 38 % of cases, an interlobar RI higher than 0.70 corresponded to a normal interlobular RI. The values of PSV, EDV, and RI did not differ significantly at interlobular level between allograft subsets with normal and elevated serum creatinine level. Both intra- and interobserver variation were higher at interlobular than at interlobar level when performing the RI. During a conventional study of renal vasculature, an underestimation of abnormal RI findings can be expected from the incidental evaluation of interlobular tracings. We recommend sonologists to pay attention in accurately locating the sample volume at interlobar-arcuate level when evaluating intrarenal RI.