Pergamon Magnetic Resonance Imaging, Vol. 13, No. 2, pp. 233-240, 1995 Copyright 0 1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0730-725X/95 $9.50 + .OO 0730-725X(94)00114-6 l Original Contribution USPIO-ENHANCED MR IMAGING OF GLYCEROL-INDUCED ACUTE RENAL FAILURE IN THE RABBIT HERON TRILLAUD , * PHILIPPE DEGR~ZE , * CHRISTIAN COMBE , t COLETTE DEMINI~RE , $ JEAN PALUSS&RE,* SORAYA BENDERBOUS,!~ AND NICOLAS GRENIER* *Service de Radiologie, HBpital Pellegrin, Bordeaux-Equipe de Recherche en Imagerie Medicale, Universite de Bordeaux 2, tService de Nephrologie, SLaboratoire d’Anatomopathologie, HGpital Pellegrin, Bordeaux, and SLaboratoire Guerbet -Aulnay sous Bois, France Enhanced-MR imaging in combination with ultrasmall superparamagnetic iron oxide (USPIO) was used in the glycerol-induced model of acute renal failure (ARF) in the rabbit to detect renal perfusion abnormalities. A con- trol group (n = 5) and an ARF group (n = 5) were studied after intramuscular injection of glycerol (10 ml/kg) with T,-weighted spin-echo sequence at 1.5 T and a 27 pmol/kg IV dose of iron. The signal intensity (SI) was quan- tified in the cortex, the outer medulla (OM), and the inner medulla (IM). In control rabbits, the maximum SI de- crease after USPIO injection was in the OM (76% f 3.6), as this is the region of maximal vascular density, then in the IM (73.4% f 2.9). In the glycerol group, SI loss in the OM (61070 f 12.6) and the IM (45.2% + 16.24) was significant less than in the control group (p < .05). Pathology results showed fibrinous tbrombus in the efferent arterioles and congestive aspect of the vasa recta in the medulla. We argue that a reduced medullary concentration of USPIO in the renal failure group is indicative of medullary bypoperfusion. Keywords: Contrast media; Kidney magnetic resonance; Kidney blood supply; Glycerol-induced acute renal failure. INTRODUCTION Intramuscular injection of glycerol in the rabbit induces a model of acute renal failure (ARF) that resembles the acute renal failure caused by massive release of myo- globin in Crush syndrome in humans.‘,’ This glycerol model in the rat and the rabbit is well-known and nu- merous studies2-5 have shown that it induces two types of lesions, that is, ischaemic lesions caused by an in- crease in vascular resistance and a decrease in renal blood flow in the first 2-6 h postinjection,3-5 and vari- able tubular obstruction.2 Ischaemia predominates in the inner cortical zone and therefore in the juxtamed- ullary nephrons ,3*5 as this region appears to be more sensitive to hypoperfusion.6*7 The efferent arterioles of the juxtamedullary glomeruli ensure capillary per- fusion in the medulla by supplying both the vasa recta and the capillary plexus. *-lo In this model of ARF, vas- cular changes occur, with a decrease in perfusion pre- dominant in the deep juxtamedullary zone of the cortex and throughout the medulla.6 The usual techniques for studying perfusion are of limited value for the medullary compartment because of the low medullary blood flow (only lo-15% of the total renal blood flow). The radioactive microsphere technique allows accurate measurement of the cortical blood flow, but these microspheres are blocked on the post glomerulary vessel and do not allow accurate mea- surement of the medullary blood flow. A non invasive method would be useful in the hemodynamic assess- ment of various vascular and parenchymal disease and in the study of the effects of vasoactive drugs. MRI can be used to monitor changes in perfusion when under- taken in conjunction with the injection of blood pool contrast agent. As the blood pool contrast agent for MRI is smaller than the radioactive microspheres, these contrast agents succeed in passing the small medul- lary vessels. RECEIVED 6/l/94; ACCEPTED g/23/94. Radiologie, HBpital Pellegrin, Place Amelie Raba-Leon, Address correspondence to Nicolas Grenier, Service de 33076 Bordeaux, France. 233