Ultrasound Focal fatty change

Focal fatty infiltration 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 (Fig. alow).
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.

A & B

Ultrasound images of Focal fatty sparing in the left lobe. This
sharply demarcated area of normal liver contrasts with
the surrounding hyperechoic fatty liver. (B) Focal fatty
infiltration anterior to the main portal vein,
characteristically ‘square’ in shape.