What is the news on the role of liver FibroScan? Is it a noninvasive diagnostic method of liver fibrosis?
| Response from Rowen K. Zetterman, MD, MACP, MACG
Professor of Internal Medicine, University of Nebraska, Omaha; Clinical Professor of Medicine, Creighton University, Omaha, Nebraska
Establishing the presence of fibrosis or cirrhosis in patients with chronic liver disease is important for assessment of prognosis and for evidence of progressive disease (fibrosis) in disorders such as hepatitis C virus (HCV) infection or nonalcoholic fatty liver disease. Currently, liver histology obtained by percutaneous liver biopsy is the "gold standard" for the presence of fibrosis or cirrhosis. Liver biopsy carries a small risk for the patient, may be associated with procedure discomfort, and interpretation can be affected by sampling error and interpreter variability.
Two noninvasive radiologic techniques to assess hepatic fibrosis have been studied. Both rely on assessment of the effect of liver stiffness (fibrosis) on the velocity of transmission of a shear wave through the liver. Ultrasound elastography, commercially known as FibroScan®, uses a modified ultrasound probe to measure the velocity of a shear wave created by a vibratory source. Estimates of stiffness of the liver by ultrasound correlate with fibrosis stage. Ultrasound elastography can be performed in approximately 95% of patients, although older patients and patients who are obese can be more difficult to study. This technique has been evaluated most consistently in patients with chronic HCV disease.
Magnetic resonance elastography assesses images of an acoustic wave generated by a sound source as it passes through the liver to determine hepatic stiffness. Both techniques are similar in assessment of fibrosis, although it has been suggested that magnetic resonance elastography may have less variability with repetitive imaging than ultrasound.Acquisition time is similar for both techniques.
Ultrasound elastography is strongly correlated with advanced fibrosis in patients with chronic hepatitis, and values above 12.5 kPa are indicative of cirrhosis. This technique works best for separating patients with minimal or no fibrosis from those with significant fibrosis. A linear correlation with increasing fibrosis has not been demonstrated, and 15% discordance between elastography scores and histologic fibrosis has been observed. Advanced fibrosis may be underestimated and patients with macronodular cirrhosis may be classified as noncirrhotic. Fibrosis may be overestimated in patients with extrahepatic cholestasis or acute hepatocellular injury[9,10] due to the effects of these conditions on liver stiffness. Ultrasound elastography does not distinguish patients with no fibrosis from patients with minimal fibrosis. Ascites can interfere with the generation of a shear wave through the liver.
In summary, ultrasound elastography will separate patients with minimal or no fibrosis from those with advanced fibrosis or cirrhosis, although it may occasionally underestimate fibrosis in some patients with advanced fibrosis or macronodular cirrhosis. Additional studies will establish the role of this technique in evaluating hepatic fibrosis in patients with chronic liver disease.
Medscape Gastroenterology © 2009 Medscape, LLC
Cite this: Rowen K. Zetterman. What Is the Role of FibroScan in Diagnosing Liver Fibrosis? - Medscape - Jun 17, 2009.