Diffuse hepatic steatosis (grading)

Last revised by Karen Machang'a on 30 Oct 2023

Grading of diffuse hepatic steatosis on ultrasound has been used to communicate to the clinician about the extent of fatty changes in the liver. 

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  • grade I: diffusely increased hepatic echogenicity but periportal and diaphragmatic echogenicity is still appreciable

  • grade II: diffusely increased hepatic echogenicity obscuring periportal echogenicity but diaphragmatic echogenicity is still appreciable 

  • grade III: diffusely increased hepatic echogenicity obscuring periportal as well as diaphragmatic echogenicity 

Steatosis is correlated with signal attenuation during liver stiffness assessment using the controlled attenuation parameter (CAP). The CAP provides extra information on ultrasonic signal attenuation during Transient Elastography examination5. This provides a standardized non-invasive measure of hepatic steatosis. The results are given in decibels per meter (dB/m).

Controlled attenuation parameter (CAP) technology for assessing steatosis:

  • s0: normal (below 184 dB/m)

  • s1: mild (184-248 dB/m)

  • s2: moderate (249-280 dB/m)

  • s3: severe (above 280 dB/m)

It is important not to fall into the pitfall that all diffusely echogenic livers are fatty, other pathologies may produce identical appearances, including cirrhosis.

Some suggest that visual grading of hepatic steatosis is subject to a wide interobserver and intraobserver variability 3. 

There is also a histological three point scale for grading severity of non-alcoholic steatohepatitis 4. These two grading systems are not currently correlated.

CAP values are influenced by a number of variables including NAFLD, diabetes, BMI, older age, presence of ascites5.

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