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Background
In the pre-transplant workup of incidental renal lesions, contrast enhanced computed tomography (CT) or magnetic resonance imaging (MRI) is routinely used to classify lesions as benign or suspicious. However, the use of intravenous (IV) contrast is often unsuitable for this patient population because of poor renal function. Contrast-enhanced ultrasound (CEUS) with intravascular microbubbles is an emerging modality which can be used to characterize indeterminate renal lesions. This modality is especially useful for those with chronic kidney disease (CKD) as this contrast medium does not utilize renal excretion as required by IV contrast agents used in CT and MRI. Several studies have shown comparable diagnostic and classification accuracy in the characterization of renal lesions in comparison to contrast-enhanced CT. Accurate diagnosis of indeterminate renal lesions is critical in the management of pre-transplant patients in order to avoid delays in transplant. Therefore, this educational exhibit aims to provide a pictorial review of CEUS appearances of a wide variety of renal pathologies found in pre-transplant assessments at our tertiary care hospital with a comprehensive renal transplant program.

Educational Goals / Teaching Points
The educational goals are to understand the utility of CEUS in a patient population in which CT and MRI contrast agents are contraindicated, understand the principle of CEUS technique and differences from CT/MRI contrast agents, and recognize the imaging features of various renal lesions on CEUS.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Exhibit will include gray scale, Doppler and CEUS images, and videos with illustrations of papillary and clear cell renal cell carcinomas (RCC), Bosniak II/hemorrhagic and simple cysts, prominent column of Bertin, etc. Ultrasound imaging was performed after IV injection of microbubbles for up to 5 minutes. Malignant lesions suspicious for RCC demonstrated arterial contrast enhancement and prompt contrast washout. Various benign lesions did not demonstrate any suspicious contrast enhancement.

Conclusion
With proper interpretation, the efficacy and accuracy of CEUS in the characterization of indeterminate renal lesions is high. Further, CEUS imaging has proven advantageous in comparison to CT and MRI regarding repeatability, affordability, and addressing the needs of challenging patients. In the pre-transplant population, CEUS proves to be an efficient diagnostic imaging technique rather than waiting for lesion size stability which can delay time to transplant.