The hemodynamics of renal circulation following cardiac systole-diastole might be detected from cortical perfusion. Purpose Based on the perfusion difference among systole-diastole, a more sensitive approach for renal function evaluation with dynamic power Doppler ultrasonography (PDUS) was pursued in this study.

With a linear probe, we obtained the serial 45 power Doppler sonograms for renal cortical vascularity in the DICOM format for 2~3 seconds with 3-4 cardiac cycles. This was obtained from one centi-meter width including inter-lobular and following terminal vessels as the region of interest (ROI) for analysis. The percentage of color pixel in ROI was defined as power Doppler vascular index (PDVI). Five indices including (1) PDVImax/PDVImin (2) mean of weighted PDVI (WPDVImean - dB) (3) total area (T - cm2) (4) small area (S - cm2) between systole-diastole and (5) S/T ratio (%) were developed in canine models of dopamine infusion (5 dogs) and induced hydronephrosis (1 dog on both kidneys for 60 days) and further applied in an allograft patient (until D 93 after surgery).

After the increase and decrease of cortical circulation were successfully identified by PDVIs in canine model, we further showed that the decreased circulation could be detected by PDVIs earlier than the change of serum creatinine in allograft patient with an episode of acute rejection. After principal component analysis, S/T ratio was the most sensitive index in PDVIs for the evaluation of renal perfusion change, and provided more information than renal resistive index did.

The disturbance of renal circulation was initiated by decreased diastolic perfusion in conjunction with special renal vascular architecture. The change of post-glomerular capillary circulation could be early detected with dynamic PDUS and PDVIs which can override the clinical application of serum creatinine for early diagnosis of renal diseases in the near future.