Facts: Fatty Liver
- Most common abnormality of the liver seen on cross-sectional imaging
- Common patterns: diffuse fat accumulation, diffuse fat accumulation with focal sparing, and focal fat accumulation in an otherwise normal liver
- Unusual patterns may mimick neoplasm, inflammation or vascular conditions
- Pathology: triglyceride acculation within cytoplasm of hepatocytes
- Term "fatty liver" is preferred over "fatty infiltration of the liver" because triglyceride accumulation occurs within hepatocytes but rarely other cell types. Infiltration of fat into parenchymal does not occur
- US: 1) Liver echo greater than renal cortex and spleen with attenuation of sound wave, 2) loss of definition of diaphragm, 3) poor delineation of intrahepatic architecture (to avoid false-positive diagnosis, all three findings should be fulfilled). Sensitivity 60-100%. Specificity 77-95%.
- CT: Liver attenuation 10 HU less than that of spleen, or less than 40 HU. Sensitivity 43-95%. Specificity 90%.
- MRI: Signal intensity loss on opposed-phase images in comparison with in-phase images. Sensitivity 81%. Specificity 100%.
- Diffuse deposition: most common
- Focal deposition and focal sparing: characteristically in specific areas (adjacent to falciform ligament or ligamentum venosum, porta hepatis, in GB fossa). Suggestive findings of fatty pseudolesions rather than true masses are:
- Fat content
- Characteristic location
- Absence of mass effect on vessels and other liver structures
- Geographic configuration (not round or oval)
- Poorly delineated margin
- Contrast enhancement similar to or less than that or normal liver parenchyma
- Multifocal deposition
- Perivascular deposition
- Subcapsular deposition
Hamer OW, Aguirre DA, Casola G, et al. Fatty liver: imaging patterns and pitfalls. Radiographics 2006;26: 1637-1653.