Transplant renal artery stenosis. Evaluation of diagnosis with magnetic resonance angiography compared with color duplex sonography and arteriography.

The goal of this study was to assess the value of a three-dimensional phase contrast magnetic resonance angiography (3D PC MRA) for diagnosing transplant renal artery stenosis (TRAS). Twelve consecutive patients clinically suspected of having TRAS were prospectively enrolled during a period of 18 months. Delays from transplantation varied from 3 months to 4 years (mean: 18.3 months). Patients first had color Doppler sonography, then MRA-and, on the following day, intraarterial digital subtraction angiography (IADSA). The site of the maximum peak systolic velocity was noted when doing the report of each color Doppler sonogram. On MRA images, any signal cutoff or any vascular narrowing of more than 50% of the diameter of the vessel was considered to be a significant stenosis. Eight patients were considered to have TRAS on MRA, but only two stenoses were noted on IADSA. The six false-positive results of MRA (due to major intravoxel phase dispersion) were observed when elevated peak systolic velocities were noted on doppler sonograms (mean: 214 cm/sec). These elevated peak systolic velocities were noted in the proximal part of the renal artery when there was a tortuous vessel or a sharp angle between the renal artery and the parent vessel. It is our opinion that 3D PC MRA is of limited value for the diagnosis of renal transplant artery stenosis because of a high number of false-positive results.