Valproic acid-induced hyperammonaemic coma and unrecognised portosystemic shunt.

Hyperammonaemic encephalopathy is a rare and potentially fatal complication of valproic acid treatment. The clinical presentation of hyperammonaemic encephalopathy is wide and includes seizures and coma. We present a case of hyperammonaemic coma precipitated by sodium valproate use for symptomatic epilepsy in a patient with unrecognised portosystemic shunt, secondary to earlier alcoholism. The absence of any stigmata of chronic liver disease and laboratory markers of liver dysfunction delayed the recognition of this alcohol-related complication. The portal vein bypass led to a refractory, valproic acid-induced hyperammonaemic coma. The patient fully recovered after dialysis treatment.