Monitoring of renal allografts by Doppler ultrasound: precision and reference values

The Doppler ultrasound method was used to obtain blood flow velocity curves from one of the large segmental arteries near the pelvis of transplanted renal allografts. The precision of the method for estimation of the pulsatility index (PI), the ratio between the peak systolic and the least diastolic velocity (A/B ratio) and the ratio of the are under the velocity curve of the first half and the second half of the cardiac cycle (AUC 1/2 ratio) was tested in vivo by examination of six renal allograft patients eight times. Two investigators examined each patient twice in random order upon two successive days. To investigate variation with time the same 10 patients were examined four times with 6-8 week intervals. To establish normal ranges for the PI, the A/B ratio and the AUC 1/2 ratio, a cross-sectional study of 54 patients with stable and well-functioning renal allografts was performed. No systematic variation was found between observers, days or repeated observations. The mean coefficient of variation was 8.3% for the pulsatility index, 5.8% for the A/B ratio and 14.9% for the AUC 1/2 ratio. The longitudinal study showed no systematic variation of the indices with time. For the 54 patients in the cross-sectional study the mean pulsatility index was 0.78, the mean A/B ratio 2.62 and the mean AUC ratio 1.82.