To compare, in terms of their feasibility and normal range, 99mTc-DTPA renal perfusion imaging and renal perfusion imaging using harmonic ultrasound (US) with a microbubble contrast agent for the evaluation of renal perfusion after renal transplantation.

During a six-month period, thirty patients who had received a renal transplant underwent both 99mTc-DTPA renal perfusion imaging and renal perfusion imaging using harmonic US with a microbubble contrast agent. Sonographic renal perfusion images were obtained before and after a bolus injection of the microbubble contrast agent LevovistTM (SH U 508A; Schering AG, Berlin, Germany) every 3 seconds for 3 minutes. Sonographic renal perfusion images were converted into a renal perfusion curve by a computer program and Tpeak of the curve thus obtained was compared with that of the 99mTc-DTPA curve.

Average Tpeak of the 99mTc-DTPA renal perfusion curve was 16.2 seconds in the normal group and 39.6 seconds in the delayed perfusion group, while average Tpeak of the sonographic renal perfusion curve was 23.7 seconds and 46.2 seconds, respectively. Tpeak of the sonographic renal perfusion curve showed a good correlation with that of the 99mTc-DTPA curve (correlation coefficient=0.8209; p=0.0001). The cut-off value of Tpeak of the sonographic renal perfusion curve was 35 seconds (sensitivity=90%, specificity=95%).

In patients who have received a renal transplant, the findings of renal perfusion imaging using harmonic US with a microbubble contrast agent show close correlation with those of 99mTc-DTPA renal perfusion imaging. The optimal cut-off value of Tpeak of the sonographic renal perfusion curve was 35 seconds.