Renal diffusion and BOLD MRI in experimental diabetic nephropathy

Abstract

Purpose To investigate the possibility of using combined blood oxygen level‐dependent (BOLD) imaging and diffusion‐weighted imaging (DWI) to detect pathological and physiological changes in renal tissue damage of the kidney induced by chronic renal hyperfiltration. Materials and Methods The apparent diffusion coefficient (ADC) and the T₂* value within the inner compartments of the kidneys of 17 rats with diabetes mellitus were compared with the results obtained from a control group (N = 16). The influence of dynamic changes of the renal function on the blood‐oxygen saturation was evaluated by comparing the T₂* values before and after the active reduction of tubular transport by furosemide injection. Results All compartments of the diabetic kidney showed significantly (P < 0.05) lower T₂*‐values compared to the control group. In particular, the very low values in the outer stripe (OS) of the outer medulla (OM) (T₂*‐normal: 69.4 ± 10.9 msec; T₂*‐diabetic: 51.4 ± 13.9 msec) indicated either hypoxia due to hyperfiltration, or renal blood volume changes. Diffusion imaging of the same area showed significantly lower ADC values (ADC‐normal: 1.45 ± 0.26; ADC‐edema: 1.19 ± 0.25 [10^–9m²/s]) that correlated with pathological findings on histopathology. The injection of furosemide significantly (P < 0.05) increased T₂* in all compartments of both populations while the ADC remained unchanged. Conclusion BOLD‐contrast imaging appears to be able to depict tissue at risk from ischemia by revealing information about the balance between tubular workload and delivery of oxygen, and thus may reflect a measure of the reserve capacity. The diffusion measurements apparently reveal J. Magn. Reson. Imaging 2003;17:104–113.