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E1509. Bubbles in the Beans: A Tutorial of How to Perform and Interpret Contrast-Enhanced Ultrasound (CEUS) in the Kidneys
Authors
  1. Neema Patel; Mayo Clinic
  2. Lauren Alexander; Mayo Clinic
  3. Nirvikar Dahiya; Mayo Clinic
  4. Shweta Bhatt; Mayo Clinic
  5. Melanie Caserta; Mayo Clinic
Background
Contrast-enhanced ultrasound (CEUS) is an inexpensive technology that is growing in practice and helps differentiate incidentally detected renal lesions on cross-sectional imaging as cystic versus solid in order to guide appropriate management. Intravenous (IV) administration of ultrasound contrast agents (UCA) can help evaluate enhancement characteristics of a variety of lesions throughout the body. UCAs have been widely utilized "off-label" agent to evaluate the kidneys. CEUS has several advantages in renal evaluation, including no nephrotoxicity, no use of ionizing radiation, quick real-time dynamic capabilities, and a strong safety profile.

Educational Goals / Teaching Points
Present a cased-based review of CEUS of native and transplant kidneys to review basics and focus on technique(s) of how to perform renal CEUS. Discuss indications/contraindications, advantages/disadvantages, and technical limitations of renal CEUS. Review CEUS cases of benign and malignant lesions in native kidneys and evaluate transplant kidneys with static and cine sonographic images and ultrasound enhancement characteristics.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
CEUS uses safe, low-solubility, and compressible gas microbubbles (1-7 micrometers) in a biomaterial shell that remain in the intravascular space and serve as an excellent UCA that provides high spatial and temporal resolution. This enables good evaluation of the renal parenchyma, vasculature, and renal lesions. The gas is exhaled in 10-15 minutes post-injection, and the liver metabolizes the shell. The microbubbles create images via a nonlinear response with pulse inversion technique. Various techniques such as flash pulsation and color flow have beneficial application in allowing real-time interpretation and problem solving of renal lesions. CEUS has various advantages including short half-life of the UCA that enables multiple injections that are good for serial imaging. CEUS is safe with rare and mild adverse events. There is no nephrotoxicity or ionizing radiation involved, and it can be performed portably that is helpful for patients with renal failure, contrast allergy issues, or cannot have CT or MRI. Few disadvantages or contraindications include requiring intravenous access placement, contrast specific software required, the ability to handle large amount of data and images, and issues with patients who are pregnant, nursing, or have hypersensitivity reactions. Limitations with CEUS include large body habitus, small lesion size, penetration issues for lesions over 10 cm deep, or patients with multiple lesions. This exhibit will review the technique and physics as well as imaging findings of enhancement patterns via a case-based review of renal CEUS with a special focus on problem-solving of renal lesions and renal transplant issues.

Conclusion
CEUS is a safe, effective, and useful tool for real-time diagnostic evaluation and serial imaging of indeterminate renal masses that helps guide clinical management, especially in patients with poor renal function. Increased utilization of renal CEUS will play an important role and improve evaluation of native and transplant kidneys.