Doppler signal quantitation in renal allografts: comparison in normal and rejecting transplants, with pathologic correlation.

Quantitative duplex Doppler sonography was performed in 55 renal transplant patients during 54 independent episodes of acute rejection, three episodes of chronic rejection, three episodes of acute tubular necrosis (ATN), and 23 occasions of normal graft function. Doppler signals were obtained from four arterial sites in each kidney. Nine patients, in whom signals were absent, were subsequently shown at nephrectomy to have absence of perfusion resulting from severe acute vascular rejection. In each patient with graft dysfunction, biopsy or nephrectomy was performed within 24 hours of the Doppler study. Arterial Doppler signals were quantified using a pulsatility index (PI). Acute rejection produced a significantly higher PI at each arterial site. Receiver-operator characteristics suggest that signals obtained from the segmental arteries are most sensitive to these changes. With a threshold PI of 1.5, the sensitivity of this technique for detection of acute renal allograft rejection is 75%; the specificity is 90%. In acute vascular rejection, the same PI yields a sensitivity of 79% and specificity of 90%. With a cutoff PI of 1.8, a specificity of 100% can be achieved.