Functional Imaging of the Kidney by Means of Measurement of the Apparent Diffusion Coefficient

Purpose: To determine the relationship between the apparent diffusion coefficient (ADC) and renal function.

Materials And Methods: Twenty-three volunteers and seven pigs underwent diffusion-sensitive magnetic resonance (MR) imaging of the kidneys with a stimulated-echo acquisition mode excitation and echo-planar imaging readout under various physiologic conditions. The effect of hydration and anisotropic diffusion was studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model.

Results: The renal ADC values of dehydrated subjects were substantially increased with rehydration. Diffusion was highest in the medulla, with a pronounced radial component in the renal collecting system. In the pig model, induced renal artery stenosis resulted in immediate decrease in renal ADC; the degree of change was related to the flow deficit. The ADC also decreased with ureteral obstruction, but diuresis had no meaningful effect.

Conclusion: In vivo measurement of ADC has the potential for use as a noninvasive means to explore the functional status of the kidney.