Fine structure of the human gallbladder with cholesterosis with special reference to the mechanism of lipid accumulation.

Eight excised gallbladders with cholesterosis were studied by light and electron microscopy. Lipid droplets were found not only in the submucosa, but also in the infranuclear cytoplasm of epithelial cells. These contained well developed mitochondria and agranular reticulum. Lipid droplets were seen to form in the agranular reticulum. Macrophages were often present between the epithelial cells and the submucosa and contained numerous processes and well developed cell organelles, abundant lysosomes and lipid droplets. With the advance of lipid deposition, macrophages were filled with lipid droplets and became foam cells. It is suggested that these may become too large and rigid to pass through the endothelium of lymph vessels or that the lumen of the lymph vessels may be obstructed by large foam cells resulting in the destruction of these vessels and the accumulation of foam cells in the submucosa.