Exploring the Value of Functional Magnetic Resonance Imaging in Assessing Subclinical Renal Graft Rejection

Background: Functional magnetic resonance imaging (fMRI) is a promising method for assessing kidney injury. This study aimed to explore the value of fMRI in evaluating subclinical renal graft rejection. Methods: We analyzed a cohort of 31 kidney transplant recipients from The Second Affiliated Hospital, Nanjing Medical University, who underwent protocol biopsies and fMRI scans at 3 and 12 months after transplantation. Recipients were divided into a subclinical rejection group and a basically normal group based on pathological findings. fMRI parameters, including blood oxygenation level-dependent imaging (BOLD), intravoxel incoherent motion imaging (IVIM), and diffusion kurtosis imaging (DKI), were utilized to assess oxygenation, microcirculation perfusion, and tissue microstructural changes in renal grafts. Results: Comparing the imaging parameters of 17 cases in the subclinical rejection group with 29 cases in the basically normal group, we found significant differences in cortical apparent transverse relaxation rate (R2*), cortical axial diffusion (Da), cortical axial kurtosis (Ka), medullary fractional anisotropy (FA), and medullary Da. Cortical Ka and medullary Da were identified as independent predictors of subclinical renal graft rejection. Using MRI parameters alone, the AUC was 76.1%, with a sensitivity of 88.2% and specificity of 75.5%. For clinical indicators alone, the AUC was 73%, with the same sensitivity (88.2%) but lower specificity (58.6%). When combining MRI parameters with clinical indicators, the AUC increased to 81.3%, with a sensitivity of 76.5% and specificity of 86.2%. Conclusion: fMRI can provide critical imaging information for detecting subclinical renal graft rejection. The combined analysis of fMRI parameters and clinical indicators may enhance the identification of subclinical rejection, offering a novel approach for non-invasive rejection screening. Funding: Government Support – Non-U.S.