Noninvasive measurement of extraction fraction and single-kidney glomerular filtration rate with MR imaging in swine with surgically created renal arterial stenoses.
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.
Coulam
Curtis H
CH
Department of Radiology, Stanford University School of Medicine, 300 Pasteur Dr, H-1307, Stanford, CA 94305, USA.
Lee
Jin H
JH
Wedding
Kristin L
KL
Spielman
Daniel M
DM
Pelc
Norbert J
NJ
Kee
Stephen T
ST
Hill
Bradley B
BB
Bouley
Donna M
DM
Derby
Geraldine C
GC
Myers
Bryan D
BD
Sawyer-Glover
Anne M
AM
Sommer
F Graham
FG
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