Histopathological characteristics of hepatic lipogranulomas with portosystemic shunt in dogs

In the canine liver with portosystemic shunts (PSS), focal lesions consisting of cells with cytoplasmic brown pigments and lipid vacuoles are often observed in the hepatic parenchyma. Termed lipogranulomas, their histopathological characteristics have been little studied. In the present study, we examined liver biopsy samples from 144 dogs (age: 3 months-16 years; 65 PSS and 79 non-PSS cases), and investigated the histopathological characteristics, incidence, and density of lipogranulomas. Lipogranulomas were detected histopathologically in 55.4% of PSS dogs. The lesions were then grouped into 3 types according to the amount of cytoplasmic lipid vacuoles and brown pigments. The pigments were positive for Berlin blue, PAS, and Sudan black B, but negative with the Hall method. The majority of the cells were immunohistochemically positive for macrophage scavenger receptor, class A (MSR-A), while no cells were positive for hepatocyte-antigen and albumin. The cytoplasmic pigments were recognized as electron-dense microgranular materials by electron microscopy. The incidence of lipogranulomas was significantly higher in the PSS group than non-PSS group when dogs less than 1 year old were excluded. The lipogranuloma density in the liver was significantly higher in the PSS group. It is concluded that lipogranulomas are frequently observed in liver biopsies of canine PSS especially in dogs more than 1 year old. The lesions consisted of Kupffer cells and/or macrophages, and the cytoplasmic brown pigments are ceroid and hemosiderin. The pathogenesis of lipogranuloma in PSS needs to be clarified.