Renal cell carcinoma and renal angiomyolipoma: differential diagnosis with real-time contrast-enhanced ultrasonography.

Objective: The purpose of this study was to evaluate the usefulness of contrast-enhanced ultrasonography (CEUS) in differentiating renal cell carcinoma (RCC) from renal angiomyolipoma (RAML).
Methods: One hundred nineteen patients with 126 renal lesions (33 RAMLs and 93 RCCs) who had undergone CEUS were retrospectively studied. All of the lesions were histopathologically or clinical proved. Contrast-enhanced ultrasonography was performed using low-acoustic power modes and a sulfur hexafluoride-filled microbubble contrast agent. The baseline sonograms and CEUS images were retrospectively analyzed in consensus by 2 radiologists. The tumor echogenicity, enhancement patterns, and degree of enhancement at different phases were evaluated. The diagnostic efficacy of CEUS in differentiating the two diseases was computed and compared.
Results: On CEUS, the features of wash-out from hyperenhancement or isoenhancement to hypoenhancement over time (observed in 3.0% of RAMLs and 71.0% of RCCs; P < .001), heterogeneous enhancement (observed in 12.1% of RAMLs and 74.2% of RCCs; P < .001), and an enhanced perilesional rim (observed in 3.0% of RAMLs and 79.6% of RCCs; P < .001) achieved significant difference between RCCs and RAMLs. Early wash-out and heterogeneous enhancement or peritumoral rim enhancement yielded the highest diagnostic capability in differentiating RCC from RAML. The corresponding sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 88.2% (82 of 93), 97.0% (32 of 33), 98.8% (82 of 83), 74.4% (32 of 43), and 90.5% (114 of 126), respectively.
Conclusions: The CEUS features of early wash-out, heterogeneous enhancement, and an enhanced peritumoral rim highly suggest RCC, whereas homogeneous enhancement and prolonged enhancement are characteristic manifestations of RAML. Contrast-enhanced ultrasonography is valuable in differentiating RCC from RAML.