Contrast-enhanced ultrasound (CEUS) represents one of the most interesting and promising examples of imaging application in clinical practice. Ultrasound contrast media are defined as “blood pool” agents because they remain confined into blood vessels without reaching the excretory tract. They are classified into first and second generation depending on the gas in microbubbles. When the ultrasound beam hits microbubbles in the blood flow, their compressible gas cores oscillate in response to the high-frequency sonic energy field. The microbubbles reflect a unique echo that stands in stark contrast to the surrounding tissue due to the orders of magnitude mismatch between microbubble and tissue echogenicity. Both contrast generations are characterised by an excellent safety profile, with rare hepatic and central nervous system side effects and absent nephrotoxicity thanks to their predominant pulmonary clearance. The clinical utility of CEUS, which is widely recognised in the study of liver diseases, is also becoming relevant to the pathology of other organs, such as genitourinary system, gastrointestinal tract, peripheral vascular system, spleen and lymph nodes, and breast, lung, and endocrine and exocrine glands. Possible applications of CEUS in nephrology include renal ischemia, differential diagnosis of cystic and solid lesions, follow-up of ablative therapies, kidney trauma, kidney transplant, inflammatory diseases, renal artery stenosis, and vesicoureteral reflux.
