2006-04-26-11 Abnormal intrahepatic connections ©  De Crespigny www.thefetus.net/

* * Department of Obstetrics and Gynecology, Royal Womens" Care Hospital, Carlton, Australia

** TheFetus.net

Abnormal hepatic vascular connections are a group of anomalies that includes the abnormal connection between the hepatic arteries and portal veins or systemic veins. These shunts anomalies can be seen in a routine scan using color Doppler. Color Doppler helps to locate the abnormal vessels and to evaluate the existing connections.

The main vascular malformations are:

• Porto-systemic Shunts
• Arteriovenous Malformations
• Arterioportal Fistulas

All these anomalies have to be differentiated from the infra-diaphragmatic total anomalous pulmonary venous connections.

Porto-systemic Shunts

Definition: The portosystemic shunts are abnormal connections between the portal vein and the hepatic vein. Congenital portosystemic shunting has been recognized as an important disorder in children and should be differentiated from metabolic deficiencies. They can be extra or intrahepatic.

Extrahepatic Portosystemic Shunts

Extrahepatic Portosystemic Shunts are also called Abernethy malformations. They can be divided in two types:

• Type 1: there is a congenital absence of the portal vein and a complete diversion of the portal blood into the vena cava;
• Type 2: the portal vein is intact but some of the portal flow is diverted into the vena cava through an extrahepatic communication.

Associated anomalies: Some associated anomalies can be diagnosed as heterotaxy, Goldenhar syndrome, biliary atresia, mental retardation, and genitourinary malformations.

Ultrasound findings: The most important ultrasound finding is the absence of the portal vein. The abnormal portosystemic shunt should be searched.

Intrahepatic Portosystemic Shunts:  Intrahepatic portosystemic shunts are abnormal intrahepatic connections between branches of the portal vein and the hepatic veins.

They had been categorized into four morphological types accordingly to Park el al:

• Type 1: most common type and it consists of a single large tube that connects the right portal vein to the inferior vena cava;
• Type 2: This is characterized by a localized peripheral shunt in which one or more communications are found in a single hepatic segment;
• Type 3: portosystemic shunt through an aneurysm. This is the most uncommon type;
• Type 4: multiple communications between peripheral portal and hepatic veins in several segments;
• Type 5: persistent ductus venosus could be considered as a fifth type of portosystemic shunt.

Ultrasound findings: Ultrasound examination demonstrates an abnormal large vessel or an aneurysm communicating the branches of the portal vein with the hepatic veins. As you can see in the case previous reported, the Doppler can help to find the exactly location of the abnormal connections. 3D scan is a fabulous tool for the study of the anomalous venous malformations. With the 3D scan and using the glass body mode (one of the options of the render mode to edit the acquired volume) all the branches of the vessels can be demonstrated.

Case report

This is a 33-year-old, primigravida, with a normal first trimester screening. She was referred to our unit at 18 weeks for a routine scan that revealed a intra-abdominal cyst, lateral to fetal stomach. It appeared to be an arterio-venosus malformation with a single feeding vessel from the umbilical vein and a single vessel returning blood to the inferior vena cava just bellow the heart. Low flow could be seen through the arterio-venosus malformation. The ultrasound findings remained unaltered until the last scan at 34 weeks.

The baby was born in good conditions at 34 weeks. There was no clinical abnormality.  After delivery an ultrasound examination revealed an abnormal communication between the portal and hepatic veins. The diagnosis was of portosystemic anastomosis type III.  The pediatrician suggested that these are usually asymptomatic and regress without treatment.  However, since a portion of the portal blood can bypass the liver, it can produce a situation analogous to esophageal varices with a risk of hepatic encephalopathy. 
 
The baby will be watched but at six weeks of age was asymptomatic.

Arteriovenous Malformations

Definition: Arteriovenous malformations are congenital anomalies of the hepatic vessels characterized by an abnormal formation of the hepatic blood vessels. Due to this abnormal formation, an arteriovenous shunt is created. There is no association with the hepatic neoplasias.

Ultrasound findings: The ultrasound findings include enlarged vessels located in one lobe of the liver. The prenatal diagnosis is difficult.

Differential diagnosis: Hemangioma. MRI imaging might be use for distinguish an arteriovenous malformation from a hemangioma.

Diagnosis: A hepatic arteriovenous malformation manifests clinically in neonates with anemia, hepatomegaly and portal hypertension. Sometimes it can also manifest in late childhood with hepatic ischemia and portal hypertension

Prognosis: Unknown

Arterioportal Fistulas

Definition: Fetal hepatic arteriovenous fistulas are rare and associated with a high mortality rate. They consist in a communication between the hepatic artery and the portal venous system. Congenital arterioportal fistulas are a rare cause of portal hypertension. They can be classified in:

• Intrahepatic
• Extrahepatic

Ultrasound findings: The most common sign is a dilatation of the hepatic artery and the segment of the portal vein where the fistula is located. Doppler is the most useful tool for making the diagnosis.

Diagnosis: Most of patients are asymptomatic within the first year of life. The symptoms as portal hypertension, splenomegaly, hypersplenism and ascites, can appear only after the first year of life. So, it is difficult to determine if the fistula is congenital or acquired.

Associated anomalies: Hereditary hemorrhagic telangiectasia, Ehlers-Danlos syndrome, and biliary atresia.

Prognosis: Congenital hepatic arterioportal fistula in infants with biliary atresia is difficult to resolve because these infants are abnormally dependent on arterial inflow, and ligation or embolization of the hepatic artery could lead to fatal hepatic necrosis.

Infradiaphragmatic Anomalous Pulmonary venous connections

Definition: Anomalous Pulmonary venous connections refer to abnormal connection between the pulmonary veins and the atria. Instead of connecting to the left atrium, the anomalous veins connect to the right atrium or one of the systemic veins.  It can be classified accordingly their location and their type:

Types:

• Total: all four pulmonary veins are involved
• Partial: less than four pulmonary veins are involved

Location:

• Supra-diaphragmatic
• Infra-diaphragmatic

In total (or complete) anomalous pulmonary venous connection, 20 to 25% are infra-diaphragmatic, connection with the portal-hepatic veins and are obstructed.  In 1/3 of cases, the connection is to the innominate vein via a vertical vein.

Associated anomalies: Associated anomalies can be found in one third of the cases and includes: atrial septal defect, hypoplastic left ventricle, heterotaxy syndromes, truncus arteriosus, coarctations and transposition of the great arteries.

Ultrasound findings: A very characteristic sign is the absence of confluence of the pulmonary veins with the left atrium. The right heart may be enlarged from the right sided increased in flow. The left heart may appear comparatively small. Finally in the infradiaphragmatic form, the pulmonary vein drain into an anomalous "vertical†vein that extends caudally to connect in the liver to the hepatic circulation Doppler helps determine the vascular nature of the tubular structure. It also helps identify the level of obstruction.

Prognosis: The prognosis depends on: the number of veins affected the degree of obstruction and the presence of associated anomalies. The total anomalous pulmonary veins return consists of progressive clinical deterioration.

References:

1.  Gallego C, Velasco M,  Marcuello P,  Tejedor D, De Campo L,  Friera A. Congenital and Acquired Anomalies of the Portal Venous System. RadioGraphics 2002; 22:141—159

2. Sozos J. Fasouliotis, MD, Reuven Achiron, Zvi Kivilevitch, MD, Simcha Yagel, MD. The Human Fetal Venous System Normal Embryologic, Anatomic, and Physiologic Characteristics and Developmental Abnormalities J Ultrasound Med 2002;21:1145—1158

3. Gallego C, Miralles M, Carlos Marin C, Muyor P, Gonzalez G, Garcýa-Hidalgo E. Congenital Hepatic Shunts. RadioGraphics 2004; 24:755—772