Contrast-enhanced sonography of the kidney.

Contrast-enhanced sonography (CEUS) is a recently introduced, promising technique in the evaluation of the kidney. CEUS allows real-time assessment of normal and abnormal renal perfusions. As a consequence of the macrocirculation analysis allowed by Doppler techniques, it is possible to obtain real-time information about microcirculation. US contrast media are not nephrotoxic and can be employed safely, even in subjects with impaired renal function. There are several clinical scenarios where CEUS may play the role of a low-cost, scarcely invasive tool, including renal tumors (with special reference to small, indeterminate masses, i.e., differentiation between carcinoma and angiomyolipoma), renal atypical cystic masses (i.e., differentiation of malignant from benign cysts and follow-up of cystic lesions managed conservatively), renal infarction, renal infections, and renal injuries. In addition, CEUS can be useful in the assessment of renal pseudotumors (including any case with possible renal mass on conventional US imaging) and has been employed in radiofrequency ablation guidance. This pictorial review illustrates the CEUS findings recognizable in a wide spectrum of renal disorders and discusses the strengths and limitations of renal imaging with CEUS.