MR Imaging Assessment of Changes in Renal Function with Renal Artery Stent Placement in Swine Jonathan K. Park, BA, Thomas K. Rhee, MD, Ty A. Cashen, PhD, Wanyong Shin, MS, Scott A. Resnick, MD, James A. Gehl, MD, Brian E. Schirf, MD, Dingxin Wang, BS, Andrew C. Larson, PhD, Timothy J. Carroll, PhD, and Reed A. Omary, MD, MS PURPOSE: To prospectively test the hypothesis that magnetic resonance (MR) imaging can detect changes in renal function at the time of renal artery stent placement in a swine model of renal artery stenosis (RAS). MATERIALS AND METHODS: In this animal care and use committee–approved study, hemodynamically significant (>50%) RAS was surgically induced in six pigs. MR imaging was employed for assessment of the anatomic and physiologic changes induced by fluoroscopically guided stent placement. With MR imaging, we assessed changes in renal blood flow (RBF), extraction fraction (EF), and single-kidney glomerular filtration rate (skGFR) during the procedure. Arterial diameter stenosis before and after stent placement was assessed with x-ray digital subtraction angiography (DSA). Mean changes in functional and anatomic parameters were compared with the Wilcoxon matched-pairs test, with an  level of 0.05. RESULTS: There was no significant change in mean RBF after stent deployment (P  .44). Mean EF increased from 0.19  0.08 before stent placement to 0.31  0.17 after stent placement (P  .16). Mean skGFR measurements were 25 mL/min  16 before stent placement and 41 mL/min  28 after stent placement (P < .05). According to x-ray DSA measurements, mean stenosis measurements were 60%  12% before stent placement and 24%  16% after stent placement (P < .02). CONCLUSIONS: In swine, MR imaging can detect immediate changes in renal function after radiographically guided stent placement for unilateral RAS. This functional MR technique may have applications in the setting of hybrid MR/x-ray DSA procedure suites. J Vasc Interv Radiol 2007; 18:1409 –1416 Abbreviations: DSA = digital subtraction angiography, EF = ejection fraction, GFR = glomerular filtration rate, PC = phase-contrast, PTA = percutaneous transluminal angioplasty, RAS = renal artery stenosis, RBF = renal blood flow, skGFR = single-kidney glomerular filtration rate RENAL artery stenosis (RAS) is a com- mon cause of secondary hypertension and end-stage renal disease (1,2). RAS is typically treated by revasculariza- tion of the renal arteries, usually in the form of percutaneous transluminal an- gioplasty (PTA) and/or intravascular stent deployment (3). However, as a result of incomplete luminal expan- sion that may occur with PTA of ath- erosclerotic lesions, stent implantation has become preferred to PTA, particu- larly for ostial stenoses (3,4). The reference standard for the de- tection of RAS is renal x-ray digital subtraction angiography (DSA) (5). However, anatomic narrowing of re- nal arteries may not directly correlate with physiologic function (6). There- fore, consideration of physiologic and anatomic effects of arterial narrowing may provide a more complete under- standing of the clinical significance of renovascular disease. Glomerular filtration rate (GFR) is From the Departments of Radiology (J.K.P., T.K.R., T.A.C., W.S., S.A.R., J.A.G., B.E.S., D.W., A.C.L., T.J.C., R.A.O.) and Biomedical Engineering (T.A.C., W.S., D.W., T.J.C., R.A.O.), Northwestern University Feinberg School of Medicine, 448 East Ontario Street, Suite 700, Chicago, IL 60611. Received Febru- ary 13, 2007; final revision received July 31, 2007; accepted August 1, 2007. Address correspondence to R.A.O., Department of Radiology, Northwestern University Feinberg School of Medicine, 448 East Ontario Street, Suite 700, Chicago, IL 60611; E-mail: reed@northwestern.edu From the SIR 2007 Annual Meeting. J.K.P. was supported in part by Radiological Society of North America Summer Medical Student Re- search Grant. R.A.O. was supported in part by Na- tional Institutes of Health grant K08 DK60020. None of the authors have identified a conflict of interest. © SIR, 2007 DOI: 10.1016/j.jvir.2007.08.002 Laboratory Investigations 1409