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-th ree volunteers and seven pigs underwent diffusion-sensitive magnetic r esonance (MR) imaging of the kidneys with a stimulated-echo acquisitio n mode excitation and echo-planar imaging readout under various physio logic conditions. The effect of hydration and anisotropic diffusion wa s studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model. RE SULTS: 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 decreas e 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 pote ntial for use as a noninvasive means to explore the functional status of the kidney.