Detection of rejection in renal allografts. Evaluation with duplex sonography and DTPA renal scintigraphy with kidney/aorta perfusion ratios.

Duplex sonography and technetium-99m DTPA renal scintigraphy have been used to distinguish acute rejection from other forms of renal allograft dysfunction. In this study, duplex sonography and renal scintigraphy were compared as methods to detect rejection. Eighty-four episodes of renal allograft dysfunction that had concurrent duplex sonography and renal scintigraphy over a 17-month period were reviewed. During the duplex sonography examinations the resistive index (RI) was measured from the renal cortex. Scintigrams were evaluated for allograft perfusion and function. The kidney to aorta (K/A) ratio was calculated from the upstroke of the perfusion curve. All diagnoses were established by clinical criteria. Histologic proof was available in 49 cases. There were two episodes of hyperacute rejection, 30 episodes of acute rejection, 14 episodes of chronic rejection, and 38 episodes of dysfunction without rejection. Using an RI greater than or equal to 0.70, the sensitivity and specificity for detecting acute rejection were 90% and 76%, respectively, compared with 37% and 76% for renal scintigraphy. The K/A ratio was not helpful in the diagnosis of rejection.