Spontaneous Multiple Focal to Massive Hepatic Necrosis in Guinea Pigs

One hundred and eleven cases of multiple focal to massive hepatic necrosis were noted out of 202 guinea pigs, aged between 4 and 23 weeks, purchased from 3 different Japanese breeding colonies. Guinea pigs with hepatic lesions showed no abnormal clinical symptoms. The occurrence of lesions peaked at 5 weeks of age in males, and 10 weeks of age in females. Grossly, yellowish white lesions, up to 10 mm in diameter, were observed singly or scattered in the liver. Histopathologically, the commonest lesions consisted of coagulative necrosis or vacuolation of hepatocytes in the central area, and macrophage/lymphocyte infiltration and regeneration of bile ducts around the peripheral area. The cytoplasm of the necrotic hepatocytes and macrophages often contained mineral granules, which were thought to be the dystrophic mineralization and associated with a concomitant occurrence of chronic nephropathy. The other organs examined revealed no significant lesions related to the hepatic lesions. Light and electron microscopic examinations failed to uncover causal organisms; an experimental infection by inoculation of extract from the guinea pig hepatic lesions to immuno-suppressed mice failed to cause hepatic lesions.