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.