title: Noninvasive measurement of extraction fraction and single-kidney glomerular filtration rate with MR imaging in swine with surgically created renal arterial stenoses.
abstract: OBJECTIVE
  To test whether magnetic resonance (MR) imaging enables accurate measurement of extraction fraction (EF) in swine with unilateral renal ischemia and to evaluate effects of renal arterial stenosis on EF and single-kidney glomerular filtration rate.
  
  
  METHODS
  High-grade unilateral renal arterial stenoses were surgically created in eight pigs. Direct measurements of renal venous and arterial inulin concentration provided reference standard estimates of single-kidney EF. Pigs were imaged with a 1.5-T imager to estimate EF, renal blood flow, and glomerular filtration rate. A breath-hold inversion-recovery spiral sequence was used to measure T1 of blood in the infrarenal inferior vena cava and renal veins after intravenous administration of gadopentetate dimeglumine, and these data were used to calculate EF. Cine-phase contrast material-enhanced imaging of the renal arteries provided quantitative renal blood flow measurements. Bilateral single-kidney glomerular filtration rate was then determined: glomerular filtration rate = renal blood flow x (1 - hematocrit level) x EF.
  
  
  RESULTS
  A statistically significant linear correlation was found between EF, as determined with MR imaging, and inulin (r = 0.77). As compared with kidneys without renal arterial stenosis, kidneys with renal arterial stenosis showed 50% (0.14/0.28) EF reduction (P <.01) and 59% glomerular filtration rate reduction (P <.01).
  
  
  CONCLUSIONS
  MR imaging shows promise for in vivo measurement of EF and glomerular filtration rate, which may be useful in assessing the clinical importance of renal arterial stenosis.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr, H-1307, Stanford, CA 94305, USA.
authors.forename: Curtis H
authors.initials: CH
authors.lastname: Coulam
authors.forename: Jin H
authors.initials: JH
authors.lastname: Lee
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Wedding
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Spielman
authors.forename: Norbert J
authors.initials: NJ
authors.lastname: Pelc
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Kee
authors.forename: Bradley B
authors.initials: BB
authors.lastname: Hill
authors.forename: Donna M
authors.initials: DM
authors.lastname: Bouley
authors.forename: Geraldine C
authors.initials: GC
authors.lastname: Derby
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Myers
authors.forename: Anne M
authors.initials: AM
authors.lastname: Sawyer-Glover
authors.forename: F Graham
authors.initials: FG
authors.lastname: Sommer
mesh_terms: D000818:Animals; D005919:Glomerular Filtration Rate; D007668:Kidney / Q000473:pathology* / Q000503:physiopathology*; D007677:Kidney Function Tests; D008279:Magnetic Resonance Imaging; D012077:Renal Artery / Q000601:surgery; D012078:Renal Artery Obstruction / Q000503:physiopathology*; D013552:Swine