Magnetic resonance diffusion tensor imaging applied to rat model of contrast-induced acute kidney injury

OBJECTIVES: In this preclinical investigation, the feasibility of using diffusion tensor imaging (DTI) to study contrast-induced acute kidney injury (CIAKI) is explored, comparing radiographic outcomes with histopathologic and immunohistochemical findings after repeated animal exposures to iodinated contrast agent. MATERIALS AND METHODS: Forty-five male wistar rats were allocated to three groups (n = 15 each), each receiving two separate injections 1 day apart: group 1 (iodixanol then saline); group 2 (iodixanol twice); and control group (saline twice). Five rats were then randomly selected from each group at three separate time points (1 h, 24 h, and 120 h) for magnetic resonance imaging (MRI). Upon MRI completion, the animals were sacrificed, examining renal tissue and serum creatinine level. DTI data served to calculate fractional anisotropy (FA) and apparent diffusion coefficient (ADC). RESULTS: FA values were significantly lower in group 2 than in the others. Compared with controls, FA assessments at 1 h, 24 h, and 120 h after injections commenced were significantly lower in group 2; and ADC was significantly more pronounced at 24 h. Serum creatinine levels at 24 h were markedly elevated in both groups 1 and 2. Pearson correlation analysis revealed significant negative correlations between FA (r = −0.730; p < 0.05) or ADC (r = −0.827; p < 0.05) and tubular injury and between FA (r = −0.563; p < 0.05) or ADC (r = −0.805; p < 0.05) and hypoxia-inducible factor-1α. CONCLUSIONS: Analytic approaches to DTI with better reproducibility should aid in monitoring the early pathophysiologic derangements of CIAKI, thus facilitating timely reversal of the detrimental effects.