MR imaging of renal transplants.

Fifty-six MR studies were obtained in 32 renal transplant patients, by using T1-weighted, spin-echo, and inversion-recovery pulse sequences. The findings, particularly the loss of corticomedullary differentiation, and the extent of vascular penetration into the renal parenchyma, were compared with the clinical and histologic diagnosis of transplant rejection. Thirteen MR studies on 11 patients with clinically normal renal transplants demonstrated normal corticomedullary differentiation. Renal vessels extended into the parenchyma in all 11 patients and to the cortex in 38%. In 37 MR studies on 22 patients with a clinical or histologic diagnosis of acute and/or chronic transplant rejection, the corticomedullary differentiation was normal in 8%, faint in 24%, and absent in 68%. Renal parenchymal vessels were visualized in 32%, but extended to the level of the cortex in only 8%. In 68% of the studies with transplant rejection, no parenchymal vessels were seen. When the corticomedullary differentiation was either faint or absent, the vascular pattern was normal in 6%; in 68% of cases no parenchymal vessels could be identified. We conclude the corticomedullary differentiation and the renal vascular pattern are useful parameters in the evaluation of renal transplant rejection.