Published online Jun 21, 2014. doi: 10.3748/wjg.v20.i23.7392
Revised: December 21, 2013
Accepted: January 19, 2014
Published online: June 21, 2014
Nonalcoholic fatty liver disease (NAFLD) is a frequent cause of chronic liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH)-related liver cirrhosis. Although liver biopsy is still the gold standard for the diagnosis of NAFLD, especially for the diagnosis of NASH, imaging methods have been increasingly accepted as noninvasive alternatives to liver biopsy. Ultrasonography is a well-established and cost-effective imaging technique for the diagnosis of hepatic steatosis, especially for screening a large population at risk of NAFLD. Ultrasonography has a reasonable accuracy in detecting moderate-to-severe hepatic steatosis although it is less accurate for detecting mild hepatic steatosis, operator-dependent, and rather qualitative. Computed tomography is not appropriate for general population assessment of hepatic steatosis given its inaccuracy in detecting mild hepatic steatosis and potential radiation hazard. However, computed tomography may be effective in specific clinical situations, such as evaluation of donor candidates for hepatic transplantation. Magnetic resonance spectroscopy and magnetic resonance imaging are now regarded as the most accurate practical methods of measuring liver fat in clinical practice, especially for longitudinal follow-up of patients with NAFLD. Ultrasound elastography and magnetic resonance elastography are increasingly used to evaluate the degree of liver fibrosis in patients with NAFLD and to differentiate NASH from simple steatosis. This article will review current imaging methods used to evaluate hepatic steatosis, including the diagnostic accuracy, limitations, and practical applicability of each method. It will also briefly describe the potential role of elastography techniques in the evaluation of patients with NAFLD.
Core tip: Ultrasonography is a cost-effective imaging technique for the diagnosis of hepatic steatosis in clinical practice. Magnetic resonance spectroscopy and magnetic resonance imaging are the most accurate and reliable methods of quantifying liver fat, especially for longitudinal follow-up of patients with nonalcoholic fatty liver disease. Ultrasound elastography and magnetic resonance elastography are promising imaging methods to evaluate the degree of liver fibrosis and to differentiate nonalcoholic steatohepatitis from simple hepatic steatosis.