Evaluation of renal transplant dysfunction using color Doppler sonography

Color Doppler sonography (CDS) detects changes in renal blood flow that may be useful in evaluating renal transplant dysfunction (RTD). To assess the performance of CDS as a clinical test, we reviewed results from 223 CDS measurements in 130 renal transplant recipients during a 26 month period. Spectral wave forms were characterized by pulsatility index (PI) (maximum frequency shift minus minimum frequency shift divided by mean frequency shift). In 27 individuals with stable renal function, mean PI was 1.80 +/- 0.23 (S.D.). Abnormal PI were subsequently defined as greater than two S.D. more than the mean (PI greater than or equal to 2.3). CDS performed during the early post-transplant period (n = 91) could not differentiate acute tubular necrosis (ATN), obstruction and rejection. Abnormal studies were seen in 35 of 46 instances of ATN and in three of obstruction. In 132 studies done after the postoperative period, CDS became abnormal during rejection episodes in only 45 of 71 instances (sensitivity rate of 63 per cent). When abnormal, CDS was highly suggestive of rejection, however (45 of 49, 92 per cent specificity). Cyclosporine toxicity was not associated with abnormal pulsatility (zero of seven). In 68 instances, CDS and conventional 99mTc DTPA renogram flow studies were performed together within 24 hours. CDS was more sensitive in detecting rejection but the difference did not reach statistical significance (25 of 36 versus 17 of 36). The major advantage of CDS over conventional radionuclide imaging relates to its shorter examination time, lower cost and portable capabilities. CDS will probably become the roentgenologic imaging modality of choice in renal transplantation.