In the macrovesicular type, large fat droplets balloon the liver cell, displacing the nucleus to the periphery of the cell, like an adipocyte. Triglyceride accumulates most commonly because it has the highest turnover rate of all hepatic fatty acid esters. Liver uptake of FFA from adipose tissue and the diet is unrestrained, whereas FFA disposition by oxidation, esterification, and VLDL secretion is limited. In microvesicular fatty liver, small fat droplets accumulate, cells appear foamy, and nuclei are central. Mitochondrial injury limits FFA oxidation, while apoprotein synthesis necessary for VLDL secretion is depressed, leading to triglyceride accumulation.
Liver cells are large and foamy.
Etiology Diffuse fatty change of the liver, often zonal in distribution, is associated with many clinical situations. Alcoholism, obesity, and diabetes are the most common causes of macrovesicular fatty liver in developed countries. Focal fatty change is much less common and less well recognized. These nodules of fatty liver cells are subcapsular. They are usually an incidental finding on ultrasound or CT, presenting as multiple space-occupying lesions of the liver.