Diagnostic Value of Resistive Index of Renal Transplants in the Early Postoperative Period

Abstract

Duplex ultrasonography was used in the diagnosis of acute rejection in 150 renal transplant recipients during the early post-transplant period. In 85 patients (56%) the allograft implantation had a stable postoperative course (control group) while 34 patients (23%) had no initial graft function due to acute tubular necrosis (ATN). Acute rejection occurred in 31 grafts (21%). Doppler spectra were obtained from the intrarenal arterial branches. An average resistive index (RI) was calculated from the spectra. The RI values of the control group differed significantly from those in both ATN and rejection groups. However, there was no statistical difference between the RI values of the ATN and rejection groups. Using a cutoff point of RI greater than or equal to 0.9 the sensitivity and specificity of the diagnosis of an acute rejection were 48.4 and 92.4 percent, respectively. All grafts with stable function had an RI less than 0.9. Thus, resistive index shows a poor sensitivity and a less than 100 percent specificity in the diagnosis of rejection. However, an RI greater than or equal to 0.9 is diagnostic of some kind of pathologic condition, including rejection and ATN.