Characteristics of contrast-enhanced ultrasound in distinguishing small (≤3 cm) hepatocellular carcinoma from intrahepatic cholangiocarcinoma

Contrast-enhanced ultrasound (CEUS) is highly accurate in depicting the vascularity of liver nodules. The aim of this study was to verify the characteristics of CEUS in distinguishing small (≤3 cm) hepatocellular carcinoma (HCC) from intrahepatic cholangiocarcinoma (ICC). A total of 65 patients with a liver nodule (HCC, n = 58; ICC, n = 7) smaller than 3 cm who underwent liver CEUS and pathologic confirmation were retrospectively reviewed. CEUS findings were compared with histopathologic and clinical data. Arterial-phase hyperenhancement and portal-delayed-phase wash-out on CEUS were observed in 77.6% (45/58) of HCCs and 85.7% (6/7) of ICCs. Time of arterial-phase hyperenhancement (11 seconds [6–20] vs 16 seconds [14–19], P = .008), time of portal-delayed-phase wash-out (65 seconds (15–260) vs 35 secconds (27–54), P = .002), and time interval between arterial-phase hyperenhancement and portal-delayed-phase wash-out (50 seconds [5–249] vs 19 seconds [13–35], P < .001) on CEUS were significantly different between HCCs and ICCs showing arterial-phase hyperenhancement and portal-delayed-phase wash-out. The sensitivity, specificity, positive predictive value, and negative predictive value of time interval more than 25 seconds between arterial-phase hyperenhancement and portal-delayed-phase wash-out on CEUS for the differentiation of HCCs and ICCs were 91.1%, 83.3%, 97.6%, and 55.6%, respectively. The time interval between arterial-phase hyperenhancement and portal-delayed-phase wash-out on CEUS was the most sensitive indicator in distinguishing small HCC from ICC showing arterial-phase hyperenhancement and portal-delayed-phase wash-out.