Studies of the pathogenesis of hepatic encephalopathy are hampered by the lack of a satisfactory animal model. We examined the neurological features of rats after bile duct ligation fed a hyperammonemic diet (BDL+HD). Six groups were studied: sham, sham pair-fed, hyperammonemic, bile duct ligation (BDL), BDL pair fed, and BDL+HD. The BDL+HD rats were made hyperammonemic via an ammonia-containing diet that began 2 weeks after operation. One week later, the animals were sacrificed. BDL+HD rats displayed an increased level of cerebral ammonia and neuroanatomical characteristics of hepatic encephalopathy (HE), including the presence of type II Alzheimer astrocytes. Both BDL and BDL+HD rats showed activation of the inflammatory system. BDL+HD rats showed an increased amount of brain glutamine, a decreased amount of brain myo-inositol, and a significant increase in the level of brain water. In coordination tests, BDL+HD rats showed severe impairment of motor activity and performance as opposed to BDL rats, whose results seemed only mildly affected. In conclusion, the BDL+HD rats displayed similar neuroanatomical and neurochemical characteristics to human HE in liver cirrhosis. Brain edema and inflammatory activation can be detected under these circumstances. (HEPATOLOGY 2006;43:1257–1266.)