Portohepatic vascular pathology and liver disease: diagnosis and monitoring

A number of diseases alter the normal pathophysiology of the portohepatic vascular system. The impact of these changes depends on the severity of the disease and the involvement of the entrahepatic vasculature. Cirrhosis of the liver is not a vascular disease but the effects on the liver architecture result in severe disease often accompanied by hepatic vascular changes. Alcohol abuse and viral infections are the most common causes of cirrhosis. Portal hypertension (PHT) is one of the most frequently seen sequelae of liver cirrhosis. It results in the formation of porto-systemic collateral channels which may lead to varices and hemorrhage. Primary liver cancer is also strongly associated with liver cirrhosis. Hepatocellular carcinoma (HCC) is the most common liver cancer seen in patients with cirrhosis. There are four types of HCC based on its growth patterns: infiltrative, expansive, mixed and diffuse. Raised plasma levels of alpha-fetoprotein are a characteristic of HCC. However, this marker is unreliable in patients with smaller tumors. Ultrasound is an inexpensive, non-invasive and safe diagnostic technique used to detect portal vein changes in PHT and to identify HCC lesions in the liver. Grey scale ultrasound reveals the portal vein changes and the portal-systemic collaterals which typify PHT. The technique is most useful for diagnosis or confirmation of moderate to severe disease. HCC nodules have characteristic ultrasound patterns which help in differential diagnosis. Doppler ultrasound provides functional as well as anatomical information about blood flow in the liver and is especially useful in detecting HCC and the abnormal blood vessel architecture which surrounds a tumor. However, despite their usefulness, both imaging techniques have limitations which may be improved by the use of echo-enhancing agents. Levovist(R) is a galactose-based microbubble echo-enhancing agent which has an excellent safety profile and utility in enhancing ultrasound images of the liver. It markedly improves diagnostic confidence and reduces the percentage of non-diagnostic ultrasound scans in patients with abnormal liver pathologies. The use of echo-enhanced ultrasound to diagnose liver disease may obviate the need for more expensive and invasive diagnostic procedures.