What is the role of imaging studies in the diagnosis of fatty liver disease?

Updated: Apr 12, 2018
  • Author: Emily Tommolino, MD; Chief Editor: BS Anand, MD  more...
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Noninvasive studies such as ultrasonography (US), computed tomography (CT) scanning, and magnetic resonance imaging (MRI) are useful in helping to establish a diagnosis of steatosis, as well as in finding evidence for portal hypertension; these imaging tests are also helpful in ruling out biliary dilation (eg, choledocholithiasis) in patients with a cholestatic pattern of liver test result abnormalities.

However, these imaging modalities can neither define the cause of steatosis nor reliably distinguish between benign steatosis and steatohepatitis. Benign steatosis may be focal or diffuse, whereas steatohepatitis is usually diffuse.

In patients with alcoholic steatosis, the liver appears diffusely echogenic on US. In patients with nonalcoholic fatty liver disease (NAFLD), the liver is hyperechogenic or bright. Steatosis is detected only when substantial (≥ 30%) fatty change is present. Studies in patients who are about to undergo gastric bypass surgery indicate that US has a 93% predictive value for NAFLD, with an accuracy of 76%. Patients with steatosis on US have a higher incidence of coronary artery disease and should undergo cardiac evaluation if suspicious symptoms are present. [29]

The mean CT (Hounsfield unit) count is lower in the liver than in the spleen. CT scans may be used to monitor the course of the disease on successive scans. Focal fatty lesions may be identified by dual-energy CT scans that demonstrate increased attenuation with increasing energy.

MRI may be useful for excluding fatty infiltration. Phase-contrast imaging correlates with the quantitative assessment of fatty infiltration across the entire range of liver disease. Loss of intensity on T1-weighted images may be useful in identifying focal fat. More recently, investigators indicate that two-dimensional magnetic resonance elastography (MRE) can measure shear hepatic stiffness as a biomarker of fibrosis in children with NAFLD, but further investigation is needed to better refine, validate, and integrate MRE into clinical protocols. [96]

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