Abstract
BACKGROUND: The early diagnosis of abnormalities in transplanted kidney function is crucial for timely intervention in transplant patients. Non-invasive tests play a key role in this process. This study aimed to explore the value of blood oxygenation level-dependent (BOLD) and arterial spin labeling (ASL) techniques, based on magnetic resonance angiography (MRA) examination, in evaluating early renal allograft function. METHODS: A total of 68 consecutive renal transplant recipients were prospectively recruited. Of them, 10 were excluded due to magnetic resonance imaging (MRI) contraindications, hydronephrosis, and renal artery stenosis. Finally, 58 patients were included. The recipients were separated into three groups based on their estimated glomerular filtration rate (eGFR): Group A, recipients with good renal allograft function (eGFR ≥60 mL/min/1.73 m(2)); Group B, recipients with mild-to-moderate impaired renal allograft function (30≤ eGFR <60 mL/min/1.73 m(2)); Group C, recipients with severe renal allograft function (eGFR <30 mL/min/1.73 m(2)). Some patients underwent biopsy. All patients underwent ASL, BOLD, and renal-MRA to assess the anastomotic status of the grafted renal artery and to analyze renal blood flow (RBF) and the apparent relaxation rate (R2*). RESULTS: A total of 58 patients (Group A, 29 cases; Group B, 18 cases; and Group C, 11 cases) were included in this study. Groups B and C presented with significantly decreased RBF as compared with Group A (259.74±47.52 vs. 166.50±19.79 and 112.76±32.08 mL/100 g/min). R(2)* decreased in Group B (cortical/medullary: 10.503±1.136/11.609±1.665 sec(-1)) and Group C (cortical/medullary: 9.471±0.997/10.785±1.114 sec(-1)), compared with Group A (cortical/medullary: 10.933±0.996/12.689±1.348 sec(-1)). Correlation analysis revealed that cortical RBF, cortical R(2)*, and medullary R(2)* were positively correlated with eGFR (r=0.877, 0.536, and 0.359, respectively). The higher area under the curve (AUC) of BOLD and ASL for distinguishing Group A from Group B, Group B from Group C, and Group A from Group C were 0.973 [95% confidence interval (CI): 0.936-1.000; P<0.001], 0.914 (95% CI: 0.753-1.000; P<0.001), and 0.994 (95% CI: 0.977-1.000; P<0.001), respectively, exceeding the performance of BOLD alone. CONCLUSIONS: BOLD and ASL can evaluate the different functional transplanted kidneys' oxygenation status and perfusion level. ASL demonstrates superior diagnostic efficacy compared to BOLD. BOLD combined with ASL has high value in identifying different transplanted kidney functions in the early stage.