BACKGROUND: Hepatocellular adenoma(HCA) is a rare benign tumor of the liver. It is of clinical importance to differentiate HCA from other liver tumors, especially hepatocellular carcinoma(HCC). This study aimed to evaluate the characteristic features of HCA by conventional ultrasound and contrast-enhanced ultrasound(CEUS) findings.METHODS: Twenty-six patients(10 males and 16 females; mean age 36.2±5.0 years) with 26 histopathologically proven HCAs were retrospectively identified. According to the maximum diameter of HCAs, they were divided into three groups: <30 mm, 30-50 mm, and >50 mm. Ultrasound examinations were performed with C5-2 broadband curved transducer of Philips i U22 unit(Philips Bothell, WA, USA). For each lesion, a dose of 2.4 m L Sono Vue®(Bracco Imaging Spa, Milan, Italy) was injected as a quick bolus into the cubital vein. Lesions’ echogenicity, color-Doppler flow imaging and contrast enhancement patterns were recorded.RESULTS: Grayscale ultrasound revealed that most of HCAs were hypoechoic(73.1%, 19/26). Spotty calcifications were detected in 26.9%(7/26) of the lesions. Color-Doppler flow imaging detected centripetal bulky color flow in 46.2%(12/26) of the HCAs. CEUS showed that 73.1%(19/26) of the HCAs displayed as rapid, complete and homogenous enhancement, and 53.8%(14/26) showed decreased contrast enhancement in the late phase. There was no significant difference in enhancement patterns among different sizes of HCAs(P>0.05). Centripetal enhancement with subcapsular tortuous arteries was common in larger HCAs.CONCLUSIONS: CEUS combined with grayscale and colorDoppler flow imaging helped to improve preoperative diagnosis of HCAs. The characteristic imaging features of HCAs included: rapid homogeneous enhancement and slow washout pattern on CEUS; heterogeneous echogenicity on grayscale ultrasound; and centripetal enhancement with subcapsular tortuous arteries in large HCAs. BACKGROUND: Hepatocellular adenoma (HCA) is a rare benign tumor of the liver. It is of clinical importance to differentiate HCA from other liver tumors, especially hepatocellular carcinoma (HCC). This study aimed to evaluate the characteristic features of HCA by conventional ultrasound and Contrast-enhanced ultrasound (CEUS) findings. METHODS: Twenty-six patients (10 males and 16 females; mean age 36.2 ± 5.0 years) with 26 histopathologically proven HCAs were retrospectively identified. According to the maximum diameter of HCAs, they were divided into Three groups: <30 mm, 30-50 mm, and> 50 mm. Ultrasound examinations were performed with a C5-2 broadband curved transducer of Philips U22 unit (Philips Bothell, WA, USA) Lesions’ echogenicity, color-Doppler flow imaging and contrast enhancement patterns were recorded .RESULTS: Grayscale ultrasound revealed that mos Color-Doppler flow imaging detected centripetal bulky color flow in 46.2% (12/26) of the area (73.1%, 19/26). Spotty calcifications were detected in 26.9% (7/26) of the lesions. HCAs. CEUS showed that 73.1% (19/26) of the HCAs displayed as rapid, complete and homogenous enhancement, and 53.8% (14/26) showed decreased contrast enhancement in the late phase. different sizes of HCAs (P> 0.05). Centripetal enhancement with subcapsular tortuous arteries was common in larger HCAs. CONCLUSIONS: CEUS combined with grayscale and color Doppler flow imaging helped to improve preoperative diagnosis of HCAs. The characteristic imaging features of HCAs included: rapid homogeneous enhancement and slow washout pattern on CEUS; heterogeneous echogenicity on grayscale ultrasound; and centripetal enhancement with subcapsular tortuous arteries in large HCAs.