Fatty infiltration, also called steatosis, refers to the abnormal accumulation of fat within the cells of an organ. In sonography, this term most commonly applies to the liver, where fatty infiltration is an extremely common finding. On ultrasound, a fatty liver appears brighter or more echogenic than the adjacent kidney cortex, and in more severe cases, the increased attenuation of the sound beam causes the deeper portions of the liver to appear darker than normal. Fatty infiltration can be diffuse, affecting the entire liver uniformly, or focal, creating areas that might mimic or hide masses. Causes include alcohol use, obesity, diabetes, medications, and metabolic disorders.
Sonography Term