Lipid deposits and lipo-mucosomes in human cholecystitis and epithelial metaplasia in chronic cholecystitis.

Among the inflammatory changes seen in cholecystitis, the ultrastructural alterations of the human gallbladder epithelium include lipid and lipofuscin deposits, fusions of lipid deposits and mucus-containing vesicles forming complex substructural formations called lipo-mucosomes, and microvillar changes of sparse microvilli and basal bodies. Small, lipid-laden structures, such as VLDL-like vesicles, also are fused with the mucus vesicles. Epithelial cell sloughing could liberate and add lipo-mucosomes to the biliary sludge and participate in gallstone formation. With chronic cholelithiasis, fatty degeneration of scattered epithelial cells appears to alter the epithelial lining and favors metaplastic change that could lead to other pathologic changes, including carcinoma in situ-like lesions. In addition to lipid deposition in macrophages, lipid is also incorporated in other cells and tissues of the gallbladder wall (endothelium of capillaries, smooth muscles and fibrocytes).