Portal-systemic encephalopathy after Fontan-type operation in patient with polysplenia syndrome

An 18-year-old patient, who had polysplenia and single ventricle, presented with altered mental status 9 years after a Fontan-type operation and pacemaker implantation. He underwent replacement of common atrioventricular valve and aortic valve plasty 1 year previously and has been placed on multiple medications including beta-blocker for his poor ventricular function. Blood chemistry revealed hyperammonemia of 2420 microg/l as a cause of this altered mental status disturbance. Superior mesenteric arteriography revealed large portal-systemic shunts in venous phase as a cause of hyperammonemia. To control blood ammonia level, we placed him on low protein diet, oral polymixin B, and lactulose instead of closing shunt with device. This case illustrates that portal-systemic shunt may result in hyperammonemia leading to altered mental status long after a Fontan-type operation.