title: The use of magnetic resonance to evaluate tissue oxygenation in renal artery stenosis.
abstract: Vascular occlusive disease poses a threat to kidney viability, but whether the events leading to injury and eventual fibrosis actually entail reduced oxygenation and regional tissue ischemia is unknown. Answering this question has been difficult because of the lack of an adequate method to assess tissue oxygenation in humans. BOLD (blood oxygen-level-dependent) magnetic resonance imaging detects changes in tissue deoxyhemoglobin during maneuvers that affect oxygen consumption, therefore this technique was used to image and analyze cortical and medullary segments of 50 kidneys in 25 subjects undergoing magnetic resonance (MR) angiography to diagnose renal artery stenosis (RAS). Magnetic rate of relaxation (R2*) positively correlates with deoxyhemoglobin levels and was therefore used as a surrogate measure of tissue oxygenation. Furosemide was administered to examine the effect of inhibiting energy-dependent electrolyte transport on tissue oxygenation in subjects with renovascular disease. In 21 kidneys with normal nephrograms, administration of furosemide led to a 20% decrease in medullary R2* (P < 0.01) and an 11.2% decrease in cortical R2*. In normal-size kidneys downstream of high-grade renal arterial stenoses, R2* was elevated at baseline, but fell after furosemide. In contrast, atrophic kidneys beyond totally occluded renal arteries demonstrated low levels of R2* that did not change after furosemide. In kidneys with multiple arteries, localized renal artery stenoses produced focal elevations of R2*, suggesting areas of deoxyhemoglobin accumulation. These results suggest that BOLD MR coupled with a method to suppress tubular oxygen consumption can be used to evaluate regional tissue oxygenation in the human kidney affected by vascular occlusive disease.
authors.affiliation: Division of Nephrology and Hypertension, Departments of Physiology and Pathology, Center for Magnetic Imaging Research and Department of Radiology, Mayo Clinic, W19, Rochester, MN 55905, USA. textor.stephen@mayo.edu
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Textor
authors.forename: James F
authors.initials: JF
authors.lastname: Glockner
authors.forename: Lilach O
authors.initials: LO
authors.lastname: Lerman
authors.forename: Sanjay
authors.initials: S
authors.lastname: Misra
authors.forename: Michael A
authors.initials: MA
authors.lastname: McKusick
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Riederer
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Grande
authors.forename: S Ivan
authors.initials: SI
authors.lastname: Gomez
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Romero
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D012078:Renal Artery Obstruction / Q000175:diagnosis* / Q000378:metabolism*
chemical_list: D010100:Oxygen