The magnetic resonance renogram in renal transplant evaluation using dynamic contrast-enhanced MR imaging

To assess the role of the dynamic gadolinium DTPA (Gd-DTPA) magnetic resonance (MR) renogram in differentiating various causes of renal allograft dysfunction, contrast-enhanced MR imaging studies were performed in 5 normal renal allografts, 5 patients with acute rejection (AR), and 7 patients with cyclosporine nephrotoxicity. Time-versus-signal intensity (SI) curves were plotted. Normal renal allografts showed a rapid increase and slow decay, with a definite peak in cortical (CX) SI curves (peak mean signal intensity (Amax 338.6 +/- 46.5). The outer medullary (OM) (Amax 306.5 +/- 59) and inner medullary (IM) (Amax 263.4 +/- 47.4) curves did not show a definite peak. The OM curve slowly reached a steady state and caught up with the CX curve. AR episodes were characterized by a blunted uprise and delayed peak of CX (Amax 180 +/- 70.9) and a low-amplitude vascular phase with a slow constant uprise of the inner medullary curve (Amax 120.35 +/- 42.4). The OM signal intensity curve (Amax 150.73 +/- 78) failed to catch up with the CX curve. The maximum amplitude of SI curves in CsA-induced allograft dysfunction were low, with no definite peak, and CX, OM, and IM curves ran parallel to each other with a constant gap. Dynamic Gd-DTPA, MR imaging is a noninvasive technique that shows distinct characteristics in acute rejection, cyclosporine nephrotoxicity, and normally functioning renal allografts.