Magnetic resonance imaging evaluation of renal ischaemia-reperfusion injury in a rabbit model.

NEW FINDINGS: What is the central question of this study? Renal ischaemia-reperfusion injury occurs in various clinical settings. The clinical diagnosis of ischaemia-reperfusion injury is routinely based on biochemical and haematological tests, which cannot evaluate the function of a single kidney. New magnetic resonance imaging techniques to identify the pathophysiological changes in the renal outer medulla were evaluated. What is the main finding and its importance? This study demonstrated that susceptibility-weighted imaging is a feasible non-invasive tool for imaging and evaluating physipathological changes in the renal outer medulla after ischaemia-reperfusion injury. The aim was to evaluate the feasibility of susceptibility-weighted imaging (SWI) as a tool to identify the changes in the renal outer medulla (OM) in a rabbit model of renal ischaemia-reperfusion injury (IRI). New Zealand rabbits were used (control group n = 10; IRI group n = 40). The rabbits in the IRI group were subjected to left renal artery clamping for 60 min. T2-weighted (T2WI) and SWI examinations were performed at 1, 12, 24 or 48 h after reperfusion (each n = 10). After the examinations, the kidneys were submitted to histological evaluation. The contrast-to-noise ratio (CNR) for the left renal OM was measured using T2WI and SWI. The T2WI and SWI scores of the integrity of the renal OM were evaluated. There were significant differences between T2WI CNRs and SWI CNRs in the control group and the IRI 1, 12 and 48 h time points (all P < 0.05). No significant difference was found between T2WI and SWI CNRs at IRI 24 h (P > 0.05). The mean SWI scores of renal OM in the IRI 1 and 12 h subgroups were both significantly lower than that in the control group (all P < 0.05). The only significant difference in the mean T2WI scores of renal OM was observed between the control and IRI 1 h groups (P < 0.05). Susceptibility-weighted imaging has a significant advantage in evaluation of healthy renal OM over conventional magnetic resonance imaging, and it is a feasible non-invasive tool for imaging and evaluating changes in the renal OM after IRI.