Background: The value of contrast-enhanced ultrasound (CEUS) in differentiating between renal cell carcinoma (RCC) and angiomyolipoma (AML) was analyzed. The purpose of this study was to identify the independent indicators of CEUS for predicting RCC. Methods: A total of 172 renal tumors (150 RCCs, 22 AMLs) in 165 patients underwent conventional ultrasound (CUS) and CEUS examinations before radical or partial nephrectomy, and the features on CUS and CEUS were analyzed. Results: There were significant differences in echogenicity, blood flow signals in color Doppler flow imaging (CDFI), peak intensity, homogeneity of enhancement, wash in, wash out, and perilesional rim-like enhancement between RCC and AML ( P <0.05 for all). Multivariate analysis indicated that perilesional rim-like enhancement ( P =0.035, odds ratio [OR]=9.907, 95% confidence interval [CI]: 1.169-83.971) and fast wash out ( P =0.001, OR =9.755, 95%[CI]: 2.497-38.115) were independent indicators for predicting RCC. The area under the receiver operating characteristic (ROC) curve (AUC) for perilesional rim-like enhancement was 0.838 (95% CI:0.774-0.890) with 76.7% sensitivity and 90.9% specificity, while the AUC of fast wash out was 0.833 (95% CI:0.768-0.885) with 74.7% sensitivity and 81.8% specificity. Conclusions: This study indicated that CEUS has value in differentiating RCC and AML. Present perilesional rim-like enhancement and fast wash out may be important indicators for predicting RCC. Key words: Renal cell carcinoma; angiomyolipoma; contrast-enhanced ultrasound; ultrasonography

Background: The value of contrast-enhanced ultrasound (CEUS) in differentiating between renal cell carcinoma (RCC) and angiomyolipoma (AML) was analyzed. The purpose of this study was to identify the independent indicators of CEUS for predicting RCC. Methods: A total of 172 renal tumors (150 RCCs, 22 AMLs) in 165 patients underwent conventional ultrasound (CUS) and CEUS examinations before radical or partial nephrectomy, and the features on CUS and CEUS were analyzed. Results: There were significant differences in echogenicity, blood flow signals in color Doppler flow imaging (CDFI), peak intensity, homogeneity of enhancement, wash in, wash out, and perilesional rim-like enhancement between RCC and AML ( P <0.05 for all). Multivariate analysis indicated that perilesional rim-like enhancement ( P =0.035, odds ratio [OR]=9.907, 95% confidence interval [CI]: 1.169-83.971) and fast wash out ( P =0.001, OR =9.755, 95%[CI]: 2.497-38.115) were independent indicators for predicting RCC. The area under the receiver operating characteristic (ROC) curve (AUC) for perilesional rim-like enhancement was 0.838 (95% CI:0.774-0.890) with 76.7% sensitivity and 90.9% specificity, while the AUC of fast wash out was 0.833 (95% CI:0.768-0.885) with 74.7% sensitivity and 81.8% specificity. Conclusions: This study indicated that CEUS has value in differentiating RCC and AML. Present perilesional rim-like enhancement and fast wash out may be important indicators for predicting RCC. Key words: Renal cell carcinoma; angiomyolipoma; contrast-enhanced ultrasound; ultrasonography