Clinical History
The majority of spontaneous portal-systemic shunts have been observed in patients affected with cirrhosis and portal hypertension; however, there have been some rare cases reported in patients
without cirrhosis, such as in our case. The cause of this particular type of shunt is unknown, even though it appears to be correlated to cognitive malformations or abdominal trauma. We present a
case of congenital intrahepatic portal-systemic shunt, diagnosed with an echo-Doppler, MRI and angiography, in a 41-year-old patient without a neurological repercussion of encephalopathy.
Imaging Findings
RMR: a 41-year-old female, delivered at term, showed no signs of hepatitis, jaundice, or alcohol abuse in her previous case history. The only relevant factor was the appearance of some lipothymic
episodes at the age of 30, probably correlated to a reciprocal tachycardiac crisis. An abdominal ultrasonography, performed for cystic complaints, revealed occasional findings of an unusual tubular
structure connecting the right portal vein to the vena cava in the posterior segment of the right lobe. A further echo-Doppler scan was performed, which showed an above normal portal flow (0.44 m/s)
and a slightly enlarged hepatic communal artery (7 mm); the hepatic parenchyma appeared echogenically normal and structurally homogeneous. For this reason, the patient was admitted into our ward
where she underwent an abdominal MRI, which showed evidence of a vascular malformation of about 35 mm in diameter of the VI and VII hepatic segment, related to an abnormal intrahepatic connection
between the right portal vein and the right hepatic vein. A selective angiography of the superior mesenteric artery and of the celiac trunk was also performed and confirmed, in the venous phase, the
presence of a large high-flow fistula between the right hepatic vein and the right portal vein (Fig. 1a, b). A liver biopsy, obtained from the left lobe with sonographic guidance, showed a normal
hepatic architecture. To exclude the possible presence of vascular malformations in other areas of the body, the patient underwent an MRI, which produced no pathological findings of encephalic
parenchyma referring to vascular anomalies (Fig. 2a, b). The electroencephalogram produced no pathological evidence. The blood laboratory tests all resulted normal except for the ammonia
concentration which resulted to be 98 mg/dl (the normal range is 10–50 mg/dl). In order to exclude any possible alterations brought about by portal-systemic encephalopathy, the patient
underwent a neurological examination. No evidence of alterations was observed. The neuropsychological evaluation of cognitive functions obtained through the administration of specific tests showed a
slight alteration of visual-spatial skills, as well as of medium and long-term memory, while executive functions, evaluated with the “Trial Making Test”, the “Shoop Test”, the
“Winsconsin Test”, and the “Boston Naming Test”, all resulted normal. The patient was then discharged with a restriction of dietary protein intake. At five-months followup,
the patient did not present disturbances associated with portal-systemic encephalopathy, the laboratory blood tests were normal and the ammonia concentration was found to be 75 mg/dl.
Discussion
Only 19 previous reports of portal-systemic shunt as a result of congenital anomalies have been described in the english literature (1). The formation of a portal systemic shunt is likely due to
congenital alterations to the portal venous system. Such anomalies appear to be caused by events that alter the vascular embryogenetic processes of the liver between the 4th and 10th week of
gestation, when the intrahepatic venous plexus, formed by the two vitelline veins, develop the hepatic veinous system and that of the portal vein. The possibility that these malformations are
associated with congenital cardiac and hepatic anomalies, like extrahepatic biliary atresia and congenital hepatoblastoma, supports the hypothesis that events taking place during the prenatal period
alter the normal embryogenesis of the cardiovascular and gastroenteric systems (2). Another hypothesis suggests that these shunts have a post-traumatic origin. Park et al. have classified
portal-systemic shunts into four different morphological classes. The first, which is normally encountered in cirrhotic patients suffering from portal hypertension, consists of a single large vessel
of constant diameter connecting the portal vein and the inferior vena cava. The second type consists of a peripheral shunt in which one or more connections are verified between the peripheral
branches of the portal system and the hepatic veins in one hepatic segment. The third type is a shunt between the peripheral portal branches and the hepatic veins by means of a venous aneurysm which
can be either congenital or acquired. The fourth type presents multiple connections between the peripheral portal branches and the hepatic veins (4). Our particular case would be classified as a type
II. The detection of these vascular abnormalities is very important because they could lead to a portal-systemic encephalopathy similar to that which occurs in the case of liver cirrhosis. The
failure of portal venous blood to pass through the hepatic sinusoids before the systemic circulation causes the hyperammonemia and ammonia intoxication of the brain. The physical examination, the
imaging procedures, and the neuropsychological testing techniques are the fundamental tools used to rule out the presence of portal-systemic encephalopathy. In the asymptomatic patients or those with
slight neurological manifestations, the indicated treatment is the restriction of dietary protein intake and the oral administration of lactulose. If the medical therapy fails or if the
portal-systemic shunt is associated with portal-systemic encephalopathy, embolotherapy carried out with interventional radiology is indicated. Usually, the patients with congenital portal-systemic
shunt present hyperammonemia and severe neurological symptoms (ataxia, dysarthria, asterixis, fatigue, and drowsiness). In our patient, the hyperammonemia was lower than the others and no
neurological symptoms were found. This is probably due to the low fraction of portal flow that is shunted. Sometimes, precipitating events (such as gastrointestinal hemorrhage and constipation) or
protein-rich diet, raising the level of intestinal ammonia, could reveal the congenital anomaly with hyperammonemia and neurological manifestations (2). Our case is interesting because it showed that
the congenital portal-systemic shunt can be clinically silent for a long time, implying that large communications between portal and systemic circulation are well tolerated. In conclusion, we present
a rare case of congenital portal-systemic shunt in a non-cirrhotic 41-year-old woman with hyperammonemia and no neurological symptoms associated. She is being treated with a low-protein diet and the
five-months followup confirmed the decrease in ammonemia. If the medical therapy should fail, we will consider the therapeutic embolization by retrograde transcaval catheterization as the next course
of treatment.
Differential Diagnosis List
Congenital intrahepatic portal-systemic shunt.
Final Diagnosis
Congenital intrahepatic portal-systemic shunt.
