Effect of diabetes on renal medullary oxygenation during water diuresis.

OBJECTIVES To study the effect of water diuresis on renal medullary and cortical oxygenation in patients with diabetes using blood oxygenation level--dependent magnetic resonance imaging (BOLD MRI). RESEARCH DESIGN AND METHODS Nine mild diabetic subjects (48 +/- 2.7 years of age, six women) and nine nondiabetic subjects of similar age and sex, all without known vascular or renal disease, were studied noninvasively by MRI before and during water diuresis. RESULTS Water diuresis induced an increase in medullary oxygenation in control subjects, producing a decrease in R2* (apparent spin-spin relaxation time) of 1.89 +/- 0.27 (P < 0.01), but no significant change in the group of diabetic subjects. CONCLUSIONS These findings in middle-aged diabetic subjects, which resembled those previously described in elderly subjects >65 years of age, suggest early impairment of adaptive vasodilatation within the renal medulla in diabetes.