Role of duplex Doppler sonography in diagnosis of acute allograft dysfunction-time to stop measuring the resistive index?

Measurement of vascular resistive index (RI) by duplex Doppler sonography (DDS) has been proposed as a non-invasive technique to detect the presence of acute rejection in renal allograft recipients. Our aim was to evaluate the clinical utility of this technique. From 107 patients we reviewed 159 biopsies that were performed from 1993 to 2001 for the investigation of acute allograft dysfunction. Histological findings were correlated with RI measurements by contemporaneously performed DDS. The majority of biopsies were carried out within the first 3 months post-transplantation (111/159). Sixty-eight biopsies showed acute rejection, 91 biopsies had findings other than rejection (acute tubular necrosis, CyA toxicity, recurrent GN). Using a threshold mean RI value of 0.9, the test had a specificity for acute rejection of 89%, but a sensitivity of just 6%. If the threshold was lowered the sensitivity rose, but specificity declined sharply. Average RI in the rejection group was not higher than in controls (0.73+/-0.11 vs 0.74+/-0.11, respectively). We conclude that measurement of RI by DDS does not contribute to the diagnosis of acute allograft dysfunction.