There are several sonographic changes that can be detected in the portal vein, hepatic artery, and hepatic veins in patients with portal hypertension. Within the portal vein, flow may be hepatofugal (either within the right or left branch or the main portal vein), bi-directional (alternating hepatopetal or flow toward the liver and hepatofugal or flow away from the liver), or static in which the flow is too slow to be detected with color Doppler sonography (figure 1). In cases where no flow is detected, it is important not to misdiagnose portal vein thrombosis. The hepatic artery is often enlarged and tortuous with high peak systolic and diastolic velocities. This occurs in the setting of advanced cirrhosis and decreased portal vein flow. There are also changes within the hepatic veins. The waveform frequently has a monophasic appearance with loss of the “a” wave, and low amplitude “D” and “S” waves. This is thought to be due to increased resistance to transmission of right atrial pressure changes secondary to focal hepatic vein stenoses.
