Functional evaluation of transplanted kidneys in normal function and acute rejection using BOLD MR imaging

In this study, we evaluated a large number of subjects using BOLD MRI to provide more information about oxygen metabolism in the normal function of transplanted kidneys and to distinguish acute graft rejection from normal function kidneys. This study included 122 subjects (20 volunteers, 72 patients with normal functioning transplants, and 21 patients with acute rejection), and 9 patients had normal function grafts received examination while grafts dysfunction occurred within 6 months during the follow-up. The R2 (1/s) values in the cortex and medulla as well as the R2 ratio of the medulla to cortex (R2 ratio of M/C) were recorded. The R2 values of the medulla were higher than those of the cortex in the normal function group and the volunteers which have a steep R2 ratio of M/C. All the R2 values in the acute rejection group were lower than those in the normal function grafts group (P<0.001). Moreover, in the 9 patients as normal function, the R2 values of the cortex and medulla were different from the normal function grafts, which was lower in 5 patients and was higher in the 4 remaining patients. Conversely, the R2 ratios of M/C of the 9 patients were similar to those in the normal function group. BOLD MRI shows that decreased R2 values of the cortex and medulla and R2 ratio of M/C suggest acute renal graft rejection; furthermore, a steep R2 ratio of M/C (>1.1) is an important reason for keeping clinical normal function.