Single-center study: the diagnostic performance of contrast-enhanced ultrasound (CEUS) for assessing renal oncocytoma.

The aim of the present retrospective single-center study is to evaluate the diagnostic performance of contrast-enhanced ultrasound (CEUS) in the evaluation of renal oncocytoma. Thirteen patients with histopathologically confirmed renal oncocytoma and 26 patients with histopathologically confirmed renal cell carcinoma were included in this retrospective single-center study on whom CEUS was performed between 2005 and 2015. The applied contrast agent was a second-generation blood pool agent. CEUS examinations were performed and interpreted by a single radiologist with more than 15 years of experience (EFSUMB Level 3). CEUS examinations were successfully performed in all included patients without any adverse effects. Renal oncocytomas showed varying echogenicity (46% hypoechoic, 23% hyperechoic, 8% iso-/hyperechoic, 8% isoechoic). In two cases renal oncocytoma only demarcated upon i.v. application of contrast medium. In bilateral oncocytosis, lesions presented as hyperechoic. Only 23% of renal oncocytomas showed slight vascularization using Color Doppler. No oncocytoma-specific pattern of microperfusion could be elucidated: 85% of the oncocytomas presented hyperenhancing, of whom 50% also showed delayed venous wash-out; 8% of renal oncocytomas showed venous wash-out without early arterial hyperenhancement. Within the frame of the present study and in line with the recent state of knowledge, no specific sonomorphological feature - including CEUS - could be detected allowing for adequate discrimination between oncocytoma and renal cell carcinoma.