Noninvasive and Invasive Imaging of the Liver and Biliary Tract
Magnetic Resonance Imaging
Ultrasound imaging is a common first-line tool for the screening and surveillance of hepatocellular carcinoma in patients at high risk. However, over the past years while ultrasound has become more sophisticated, other imaging modalities have also been improved to provide more sensitive tools for early detection and characterization of liver pathology. These include computed tomography (CT) and magnetic resonance imaging (MRI). While both are relatively safe, they are not without their downsides. These risks include, but are not limited to, radiation exposure and risk of contrast reaction in CT. MRI entails the use of very powerful magnets that if improperly used can cause patient and operator harm. Many patients receive gadolinium (noniodinated) contrast, which has a low risk of adverse reactions, and has been implicated to have some causal effect on the development of nephrogrenic sclerosing fibrosis in certain populations. Minimally invasive procedures including transarterial chemoembolization will be briefly discussed as well as percutaneous biliary drainage and transhepatic portovenous shunts. Endoscopic imaging of the hepatobiliary system by endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS) allows for further evaluation of abnormalities detected by noninvasive radiologic imaging. Definitive therapy can be achieved by ERCP with sphincterotomy with stone extraction for choledocholithiasis and palliative therapy by stent placement and tissue acquisition for biliary obstruction. EUS provides high resolution imaging of the hepatobiliary system, and fine needle aspiration with EUS guidance affords tissue acquisition in areas that are not easily accessible by other means. The indications, complications, and treatment modalities of ERCP and EUS of the hepatobiliary system are discussed in detail. © 2012 John Wiley & Sons Ltd.
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