SAGE-Hindawi Access to Research International Journal of Nephrology Volume 2011, Article ID 245241, 7 pages doi:10.4061/2011/245241 Review Article The Role of Imaging in the Management of Cardiorenal Syndrome Sajid Melvin George and Kambiz Kalantarinia Division of Nephrology, University of Virginia Health System, P.O. Box 800133, Charlottesville, VA 22908, USA Correspondence should be addressed to Kambiz Kalantarinia, kk6c@virginia.edu Received 23 August 2010; Accepted 4 January 2011 Academic Editor: Claudio Ronco Copyright © 2011 S. M. George and K. Kalantarinia. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Imaging of the kidney and the heart can provide valuable information in the diagnosis and management of cardiorenal syndromes. Ultrasound- (US-) based imaging (echocardiogram and renal US) is an essential component in the initial diagnostic workup of CRS. Echocardiography provides information on the structure and function of heart, and renal ultrasound is useful in diﬀerentiating between acute and chronic kidney disease and excluding certain causes of acute kidney injury such as obstructive uropathy. In this paper we overview the basic concepts of echocardiogram and renal ultrasound and will discuss the clinical utility of these imaging techniques in the management of cardiorenal syndromes. We will also discuss the role of other imaging modalities currently in clinical use such as computerized tomography and magnetic resonance imaging as well as novel techniques such as contrast-enhanced ultrasound imaging. 1. Introduction The combination of cardiac and renal disease signiﬁcantly increases the complexity and cost of health care [1]. The chronic kidney disease associated with heart failure has been recognized as an independent risk factor for morbidity and mortality [2–5]. The rate of cardiovascular mortality in the chronic kidney disease (CKD) population is 10–20 times that of those without CKD [6–8]. Recently, the Acute Dialysis Quality Initiative has published a document describing the deﬁnition and classiﬁcation of cardiorenal syndrome (CRS) [1]. According to that document, the term cardiorenal syn- drome refers to dysfunction of one organ system in presence of acute or chronic dysfunction of the other. According to the proposed classiﬁcation, CRS is divided into 5 types. Types 1 and 2 include those with reduced kidney function due to either acute (type 1) or chronic cardiac dysfunction, and CRS 3 and 4 include worsening cardiac function in face of acute or chronic kidney disease, respectively. Secondary CRSs are grouped under type 5. In this paper we will discuss the application of various imaging modalities in the diagnosis and management of CRS. 2. Ultrasonography Imaging using ultrasound waves, ultrasonography, is a noninvasive, cost-eﬀective, and widely available technology. The availability of new imaging modalities such as harmonic imaging, Doppler ultrasound for the study of blood ﬂow, three-dimensional US and the advances in the technology and design of new transducers have signiﬁcantly improved the quality of ultrasound (US) image. Currently, US imaging is the most widely used imaging modality in many ﬁelds, and indications for its use are expanding. US examination is con- sidered the imaging modality of choice in the diagnosis and management of most cardiac and renal diseases. Therefore, the main focus of this paper would be on echocardiography and renal ultrasonography. The US examination is based on interpretation of the character of the reﬂected sound waves from body tissues. The energy and the time lag at which these reﬂected US waves return and are picked up by the transducers determine the brightness and the depth of each tissue segment. The design and frequency of US transducers determine their utility in clinical imaging. In general, higher frequency probes generate images with higher resolution but because of limited