Behavior of hepatocellular adenoma on real-time low-mechanical index contrast-enhanced ultrasonography with a second-generation contrast agent

Objective. The purpose of this study was to describe the behavior of histologically proven hepatocellular adenoma (HCA) on low-mechanical index (MI) contrast-enhanced ultrasonography (CEUS). Methods. A review of the databases from 4 academic hospitals revealed 18 patients (15 female and 3 male; mean age, 40 years; range, 25-71 years) with 25 histologically proven HCA lesions who were studied with CEUS at a low MI (0.04-0.1). Results. Twenty-four of 25 lesions (96%; 95% confidence interval [CI], 80.5%-99.3%) showed high-intensity enhancement, scored as 3 on a scale of 0 to 3, whereas only 1 lesion (4%; 95% CI, 0.7%-19.5%) was scored as 2. The time of peak enhancement ranged between 10 and 19 seconds (average, 13 seconds). All but 1 of the 25 lesions (96%; 95% CI, 80.5%-99.3%) showed early homogeneous and centripetal enhancement during the hepatic arterial phase. No portal venous phase enhancement was observed in any lesion because all showed rapid wash-out (100%; 95% CI, 86.7%-100%). Twenty lesions (80%; 95% CI, 60.9%-91.1%) were found to be isoechoic to slightly hypoechoic during the portal phase, and 19 (76%; 95% CI, 56.6%-88.5%) were isoechoic to mildly hypoechoic, whereas 7 (24%; 95% CI, 11.5%-43.4%) were hypoechoic during the late phase. Conclusions. Contrast-enhanced ultrasonography is an effective technique for identifying the microvascular and macrovascular characteristics of HCA. Typically, HCA shows early (10-19 seconds) and centripetal enhancement during the arterial phase and isoechogenicity or mild hypoechogenicity during the portal phase, remaining slightly hypoechoic or isoechoic during the late phase in most cases.