Hepatic involvement in hereditary hemorrhagic telangiectasia (HHT) is highly variable and may lead to severe clinical symptoms such as heart failure. This controlled, prospective study defined sonographic criteria for hepatic involvement in HHT. Color Doppler sonography and pulsed Doppler sonography were used to study 25 patients with HHT and liver involvement, 20 patients with HHT without liver involvement, 25 patients with cirrhosis, and 25 patients without liver disease. The diagnosis of hepatic manifestation was confirmed by computed tomography and/or angiography. Liver size, parenchymal changes of the liver, vessel diameters, and flow velocities of the portal vein and the hepatic artery were determined. Resistance index (RI) and pulsatility index (PI) were calculated. The diameter of the common hepatic artery was significantly dilated without overlap between HHT patients with liver involvement and the 3 control groups (mean 11.3 +/- 2.8 mm [HHT with liver involvement], 4.6 +/- 0.9 mm [HHT without liver involvement], 4.8 +/- 1.0 mm [cirrhosis], and 4.4 +/- 1.0 mm [healthy controls], P <.001). Doppler parameters of the proper hepatic artery differed significantly (all P <.001). In all patients with HHT and liver involvement, areas with intrahepatic hypervascularization caused by dilated intrahepatic arteries were observed in varying intensity. Cardiac output significantly correlated with the diameter of the common hepatic artery (r = 0.53, P =.007) and the portal vein (r = 0.42, P =.05). In conclusion, the diameter of the common hepatic artery (>7 mm) and intrahepatic hypervascularization are suitable sonographic diagnostic parameters of HHT with high sensitivity and specificity. Dilated diameters of the hepatic feeding vessels are indicators for systemic circulatory distress in these patients.