Liver Imaging for Hepatitis C: Testing and Diagnosis
The Hepatitis C infection causes inflammation of the liver that may gradually lead to fibrosis or scarring of the liver. While the liver has some capacity to repair itself, if inflammation continues without treatment, the damage to the liver can be irreversible. Severe fibrosis may result in cirrhosis, a condition associated with a range of health complications.
Liver imaging for hepatitis C
If you have hepatitis C, your doctor will evaluate and monitor the severity of your condition by measuring the degree (or stage) of fibrosis in your liver. Conducting liver imaging for hepatitis C early can help your doctor determine the stage of fibrosis and how advanced your liver disease is. This information can be useful in determining the timing of hepatitis C antiviral therapy. For instance, if there is little progression of fibrosis, your doctor may recommend waiting for approval of a new hepatitis C treatment that may be more effective or easier to tolerate. Additionally, since a person with cirrhosis is at increased risk for developing liver cancer (hepatocellular carcinoma), knowing the stage of fibrosis can be useful in determining the need for regular cancer screening.
Methods of evaluating fibrosis
Your doctor has several options for assessing fibrosis. Liver biopsy is an invasive method (invasive means that a sample of your liver tissue is taken). There are limitations with this procedure, including the risk for complications and the ability to sample only a small portion of the liver. For a long time, liver biopsy was considered the “gold standard” for evaluating the severity of chronic hepatitis C. However, this invasive method is slowly being replaced by newer, noninvasive tests.
Several noninvasive tests are available for assessing the degree of fibrosis in the liver. There are two general types of noninvasive tests for fibrosis1:
- Blood tests
- Imaging tests
Noninvasive methods for assessing fibrosis can be used at the time you are diagnosed with hepatitis C to determine the likelihood of significant fibrosis. They can also be used before and after treatment to determine whether fibrosis has progressed. Imaging and blood tests can be used alone or in combination to assess fibrosis. While the accuracy of these noninvasive methods has improved greatly since they were introduced and they are now commonly used by many doctors, they have not yet completely replaced liver biopsy as the standard of fibrosis assessment.
Determining the stage of fibrosis
Noninvasive methods of assessing fibrosis are used to predict the severity of fibrosis. Similar to liver biopsy, these noninvasive techniques use scoring systems such as the 5-point Metavir scoring system to determine the stage of fibrosis. A Metavir score of 2 or greater is indicates significant fibrosis.1
Blood tests are the most widely available noninvasive method for assessing fibrosis. They are quick, painless, and relatively inexpensive. A variety of different blood tests (sometimes called panels) are available for assessing liver fibrosis. These tests measure levels of various chemicals and substances (also called serologic markers) that are present in blood when there is chronic inflammation and fibrosis of the liver. Examples of some of the serologic markers used in fibrosis test panels include liver enzymes aspartate aminotransferase (AST) and alanine aminotransferase (ALT), bilirubin, several different blood proteins (globulins), and various types of collagen and cytokines. Elevations of these serologic markers can be used to predict the extent and degree of fibrosis.1
Imaging tests, including ultrasound-based elastography (eg, Fibroscan), magnetic resonance elastrography (MRE), and computed tomography (CT), are less widely available than blood tests, but have also been shown to be useful in assessing fibrosis. These imaging techniques are effective at identifying the features of advanced liver disease, including nodule formation and portal hypertension.1Ultrasound elastography is the most commonly used and studied imaging technique for assessing fibrosis of the liver. This technique uses a probe to transmit low-frequency vibrations through the liver to measure the stiffness of liver tissue. Since fibrotic tissue is stiffer than normal tissue, vibrations travel through fibrotic tissue at a different rate than through normal tissue, resulting in ultrasound images that reveal the extent of fibrosis. Other imaging techniques similar to ultrasound-based elastography are based on the measurement of sound waves or vibrations as they pass through the liver. These include acoustic radiation force impulse (ARFI) imaging and real-time shear wave elastography (SWE).1Similar to ultrasound-based elastography, MRE uses a probe (placed against the back) to generate low-frequency vibrations. Magnetic resonance imaging (MRI) is then used to measure vibrations as they pass through the liver, revealing the extent and degree of fibrosis.1
Assessment of Fibrosis: Metavir scoring system
|2||Scarring has occurred and extends outside the areas in the liver that contain blood vessels|
|3||Bridging fibrosis is spreading and connecting to other areas that contain fibrosis|
|4||Cirrhosis or advanced scarring of the liver|