Multiparametric functional MRI for detection of early renal allograft dysfunction after kidney transplantation: a systematic review and meta-analysis.

BACKGROUND

Kidney transplantation is the gold-standard renal-replacement therapy for end-stage kidney disease, yet delayed graft function affects 5-50% of recipients and predicts chronic allograft dysfunction. Functional magnetic resonance imaging (fMRI) offers a non-invasive means to simultaneously assess allograft perfusion, oxygenation, and microstructure.

METHODS

We systematically searched PubMed, Web of Science, Cochrane Library, Embase, and MEDLINE for studies evaluating arterial spin labeling (ASL), blood oxygen level-dependent (BOLD), diffusion-weighted imaging (DWI), and intravoxel incoherent motion (IVIM) MRI in kidney transplant recipients. Study quality was appraised with QUADAS-2. Data were pooled using random-effects models, with subgroup analyses by magnetic field strength, post-transplant time, and baseline creatinine.

RESULTS

Twenty-eight studies comprising 1,956 recipients were included. ASL-derived cortical renal blood flow (RBF) discriminated normal from impaired renal function (estimated glomerular filtration rate (eGFR) ≥ 60 vs. <60 mL/min/1.73 m²; mean difference (MD) 98.48mL·min⁻¹·100 g⁻¹, 95% confidence interval (CI) 68.66-128.31; P < 0.00001; I²=57%) and correlated with eGFR (r = 0.58). BOLD identified acute rejection (lower R2*; I²=77-86%) but not acute tubular necrosis. IVIM-derived D values showed the strongest discriminatory power (MD 0.14-0.16 × 10⁻³ mm²/s; P < 0.00001; I²=0%). Substantial heterogeneity (I²=18-98%) limited conclusions for some parameters.

CONCLUSIONS

Multiparametric fMRI, particularly ASL and IVIM shows promise for detecting early allograft dysfunction. However, marked inter-study heterogeneity underscores the need for standardized protocols before clinical implementation.