We reported here four cases presenting with disturbance of consciousness over long periods of time and hyperammonemia. Two patients were on maintenance hemodialysis. Contrast-enhanced computed tomography (CT) of abdomen and balloon-occluded retrograde contrast venography revealed existence of a non-cirrhotic portosystemic shunt. Conservative treatment such as intravenous branched-chain amino acid administration and oral lactulose administration had only a modest effect in all patients. Improvements in symptoms were observed following the occlusion of the shunt path in three patients. Measurements of ammonia values would be the most important test for screening, but changes in Fischer's ratio or indocyanine green (ICG) test values were also correlated with clinical symptoms. Neurologists should keep in mind the possibility of non-cirrhotic portosystemic shunts when they encounter patients with disturbance of consciousness. They should also remember that occlusion of the shunt pathway is an effective treatment.