Intrahepatic portal-systemic venous shunt is defined as a communication between the portal and the systemic-venous circulation, measuring more than 1 mm in diameter and at least partially located inside the liver. This is a rare condition, and the etiopathogenesis is unclear. Of the various types, Type I, with patent paraumbilical veins, located in the liver, is commonly encountered in portal hypertension. Other types are much less common. Only 47 cases have been reported in the entire French and English literature. Shunts may be congenital or acquired. This report describes a case of portal-systemic encephalopathy due to a spontaneous large-caliber portal-hepatic venous shunt in the right lobe of the liver confirmed by percutaneous transhepatic portography and hepatic venous angiogram. The treatment with coil embolization was successful, and hepatic encephalopathy resolved postoperatively with normalization of ammonia level. The etiology of the shunt was unclear. Given the age of the patient, the shunt was thought to have developed spontaneously.