Impact of Hepatocellular Carcinoma Tumor Size on Sonazoid Contrast-Enhanced Ultrasound Enhancement Features

Objective The aim of the work described here was to evaluate the impact of hepatocellular carcinoma (HCC) tumor size on Sonazoid contrast-enhanced ultrasound (CEUS) enhancement features, especially in tumors with diameters ≤30 mm and <10 mm. Methods In this retrospective study, we included patients with histopathologically confirmed HCC lesions and divided them into three groups on the basis of tumor size. All patients underwent Sonazoid-enhanced CEUS examinations before surgery. B-mode ultrasound (BMUS) features and CEUS enhancement patterns were evaluated according to current World Federation for Ultrasound in Medicine and Biology Guidelines criteria. The χ2- and Student t-tests were used to compare differences between groups. Results We included 132 patients with histopathologically confirmed HCC lesions from November 2020 to September 2022. On the basis of tumor size, patients were divided into group 1 (<10 mm, n = 5), group 2 (10–30 mm, n = 54) and group 3 (>30 mm, n = 73). On BMUS, most HCCs appeared heterogeneous but predominantly hypo-echoic (61.4%, 81/132) with ill-defined margins and irregular shapes. Meanwhile, iso-echoic features were more common in small HCCs ≤30 mm (15.3%, 9/59), but a mixed hyper- and hypo-echoic appearance was more common in HCCs >30 mm (17.8%, 13/73) (p = 0.003). On Sonazoid-enhanced CEUS, all HCCs presented arterial phase hyperenhancement (APHE) (100.0%, 132/132). Most HCCs >30 mm exhibited heterogeneous hyperenhancement (86.3%, 63/73), whereas nearly one-third of small HCCs ≤30 mm exhibited homogeneous hyperenhancement (35.6%, 21/59) (p = 0.003). In the portal venous phase, there was a significantly higher proportion of washout in HCCs >30 mm (84.9%, 62/73) than in small HCCs ≤30 mm (64.4%, 38/59) (p = 0.006). During the Kupffer phase, 11 additional hypo-enhanced lesions (mean size: 14.1 ± 4.1 mm, iso-echoic on BMUS), which were also suspected to be HCC lesions, were detected in 5 patients with small HCCs ≤30 mm and 4 patients with HCCs >30 mm. All 5 cases of HCCs <10 mm exhibited APHE and late washout (>60 s). The majority (3/5, 60%) exhibited washout in the portal venous phase (70, 74 and 75 s), one case did so in the late phase (125 s) and another in the Kupffer phase (420 s). Conclusion Tumor size had a significant impact on the washout features of HCC lesions on Sonazoid-enhanced CEUS. Small HCC lesions ≤30 mm had a higher proportion of relatively late washout in comparison to larger lesions. Sonazoid-enhanced CEUS might be helpful in the detection and characterization of HCC lesions <10 mm.