FATTY LIVER DISEASE IMAGING
Category: Diagnostic Radiology
Abstract : Focal fatty change - Focal fatty infiltration - fatty liver disease imaging Fatty infiltration of the liver is a common occurrence which may affect the whole or part of the liver. It is associated with obesity and alcoholism, and can also occur in pregnancy, diabetes and with certain drugs. The deposition of fat confined to certain focal areas of the liver is related to the blood supply to that
Focal fatty change - Focal fatty infiltration - fatty liver disease imaging
Fatty infiltration of the liver is a common occurrence which may affect the whole or part of the liver. It is associated with obesity and alcoholism, and can also occur in pregnancy, diabetes and with certain drugs. The deposition of fat confined to certain focal areas of the liver is related to the blood supply to that area.
Fatty infiltration increases the reflectivity of the parenchyma, making it hyperechoic. This can simulate a focal mass, such as a metastasis. Unlike a focal lesion however, it does not display any mass effect and the course of related vessels remains constant.
It has a characteristic straight-edged shape, rectangular or ovoid, corresponding to the region of local blood supply. Foci of fatty change may be multiple or may affect isolated liver segments. The most common sites are in segment 4 around the porta, in the caudate lobe (segment 1) and in the posterior area of the left lobe (segment 3).
Focal fatty sparing
The reverse process may also occur, in which a diffusely fatty, hyperechogenic liver has an area which has been spared from fat deposition due to its blood supply. This area is less reflective than the surrounding liver and may mimic a hypoechoic neoplastic lesion, but as with focal fatty infiltration, it has regular outlines and shape and no mass effect. The most common sites for fatty sparing are similar to those for focal fatty infiltration; segment 4 just anterior to the portal vein, segment 1 (the caudate lobe) and frequently there are multiple areas throughout the liver.
Unlike a true focal lesion, fatty change does not exhibit a mass effect and normal, undisplaced vasculature can be demonstrated with colour Doppler in areas both of focal fatty infiltration and fatty sparing. The administration of a contrast agent may also help to clarify the nature of the mass, as the area under consideration will behave exactly the same as the surrounding, normal liver in its uptake of the agent.
Lipoma
The hepatic lipoma is a relatively rare, benign hepatic tumour which is very similar in nature and acoustic appearance to focal fatty change. It differs in that it is a discrete tumour of fatty deposition rather than an infiltrative process and so can exert a mass effect on surrounding vessels if large. The fat content makes the lipoma hyperechoic compared to the surrounding liver tissue.
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