Applications of contrast-enhanced ultrasound in the kidney.

Incidental discovery of renal lesions on cross-sectional imaging studies performed for other indications is not uncommon. With the increased reliance on medical imaging, the number of incidentally detected renal lesions has also grown over time. While simple cysts account for the majority of these lesions, the presence of complex features within a cystic lesion, such as septations and solid components, can present a confusing picture. Solid lesions, too, can be indeterminate, and distinguishing between benign solid masses (like lipid-poor angiomyolipomas and oncocytomas) and renal cell carcinoma affects patient management and can prevent unnecessary interventions. Indeterminate renal lesions are traditionally further characterized by multiphase imaging, such as contrast-enhanced computed tomography and magnetic resonance imaging. Contrast-enhanced ultrasound (CEUS) is a new, relatively inexpensive technique that has become increasingly employed in the diagnostic workup of indeterminate renal lesions. With its lack of nephrotoxicity, the absence of ionizing radiation, and the ability to evaluate the enhancement pattern of renal lesions quickly and in real-time, CEUS has unique advantages over traditional imaging modalities. This article provides an overview of the current clinical applications of CEUS in characterizing renal lesions, both cystic and solid. Additional applications of CEUS in the kidney, including its roles in renal transplant evaluation and guidance for percutaneous biopsy, will also be briefly discussed.