Introduction
The liver develops from epithelial and mesenchymal interactions connected to embryonic and fetal vessel networks. The vessels tend to involute (reduce) gradually both inside and outside the liver. Ductus venosus is the last vessel to involute and tends to disappear within a few days in neonates and after a few weeks in premature babies.
When one or more of these liver vessels do not involute, it forms an abnormal communication system between the portal system vein and inferior vena cava. The abnormal communication can be within or outside the liver, single or multiple, and differs in size. 1 in every 30,000 neonates develop congenital portosystemic shunts. Permanent CPSS develops among 1 in 50,000 neonates.
What Is a Congenital Portosystemic Shunt (CPSS)?
Congenital portosystemic shunts are rare complications of anatomic anomalies that cause shunting of blood between the portal vein and systemic vein without passing through the hepatic system. The shunt can cause partial or complete diversion of portal blood to systemic vessels, inducing complications. Recently, there has been an exponential increase in congenital portosystemic shunts in neonates. The condition can also be associated with other congenital anomalies.
What Are the Causes of Developing Congenital Portosystemic Shunt in Children?
Neonates with genetic disorders, particularly Down syndrome, are at risk for developing the condition. A congenital fault in the kidney, bile ducts, digestive system, bone, and brain are associated with CPSS. A congenital heart defect is most commonly associated with the shunt. Polsyspenia syndrome presents CPSS shunt in 8 % of cases.
In some fetuses, the ductus venous can be occluded or undergo agenesis (failure in organ development) due to abnormal vessels that allow the oxygenated blood from the umbilical vein to reach the fetal heart. These abnormal vessels can persist in the postnatal phase as CPSS and cause hypoplasia of portal veins.
During early infancy, there may be intrahepatic communication between the portal and hepatic vein in liver hemangioma. The communications may persist, or the hemangioma can regress to form a shunt later in the life of infants.
How Is Congenital Portosystemic Shunt Classified?
It is categorized into two types.
1. Extrahepatic Shunt or Abernethy Malformation: The shunt is seen outside the liver. It is classified further into two depending on the patency of the portal trunk and intra-hepatic portal system.
- Type 1 Extrahepatic CPSS: It is also known as congenital absence of portal vein. Liver transplantation helps cure the condition.
- Type 2 Extrahepatic CPSS: The shunt can be closed by surgical or interventional radiology procedures.
2. Intrahepatic CPSS: The shunt is located within the liver.
Both intra and extrahepatic shunts can cause the same complications and do not account for the presence of ductus venosus. Both these shunts can be present in a single neonate. Extrahepatic shunt patency can differ based on the imaging technique. Therefore, the classification does not accurately categorize the CPSS.
What Are the Symptoms of a Congenital Portosystemic Shunt in Children?
Studies have shown a female predominance for extrahepatic shunts and a male predominance for persistent ductus venosus. Some cases were diagnosed as incidental findings. Depending on the shunt type, some children demonstrate hepatic encephalopathy or liver failure. Children have reported splenomegaly (spleen enlargement), slightly elevated serum alanine aminotransferase, and serum gamma-glutamyl transferase activity.
How Is Congenital Portosystemic Shunt Diagnosed in Children?
Neonates suspected of CPSS are screened for galactosemia (increase in galactose concentration in blood) within a few days of feeding. The neonates with CPSS demonstrated high blood galactose concentration and abnormal activity of galactose metabolism enzymes. It could be because the breast milk bypasses the liver. Lab investigations revealed that prothrombin time is prolonged in children with a shunt. Also, they reported low serum albumin concentration, high ammonia, and high total serum bile acid concentration.
Radiographic findings of the shunt can differ based on the anatomical defect. Doppler ultrasound helps diagnose the port venous shunt ratio. CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) scans will help diagnose anatomic defects. Neonates born with congenital portosystemic shunt have abnormal galactosemia tests, congenital heart disease, neonatal cholestasis, and fortuitous.
How Are Congenital Portosystemic Shunts in the Neonate Managed?
Small intrahepatic portosystemic shunt between the hepatic vein and portal branches disappear within 1 to 2 years after birth. However, the large shunts, or those with extrahepatic portal vein and ductus venosus communication, can persist and cause complications.
The doctor must confirm that the CPSS shunt is not caused by liver hemangioma or portal hypertension because their treatments differ. Stunt closure is recommended if the condition does not resolve on its own. The shunts are closed percutaneously, an occlusive device is placed within the shunt to prevent compromise of portal branch development, flow of inferior vena cava and hepatic vein, and venous drainage of other organs. Depending on the size and number of communications, the shunts are closed with an Amplatzer device or coil. Ductus venosus can also be closed through this technique. If the lumen is short or wide, then surgery is advised. The surgery is performed in one or two steps to avoid further complications. A liver transplant is the last resort when all the other shunt closer techniques fail.
What Complications Develop Due to Congenital Portosystemic Shunts in the Neonate?
Some severe complications that develop are:
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Neonatal cholestasis: Children with shunts tend to have reduced perfusion of neonatal liver, which could cause neonatal cholestasis.
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Benign and malignant liver tumors have been reported in several children. Malignant tumors develop in extrahepatic shunts. Benign tumors resolve with the closure of the shunt, whereas malignant tumors might need resection along with shunt closure.
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Hepatopulmonary syndrome: Most children have the resolution of hepatopulmonary syndrome with shunt closure, frequent monitoring is necessary.
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Portopulmonary hypertension: Children presented with dyspnea or fainting. Children with unexplained portopulmonary hypertension must be evaluated for CPSS shunt.
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Encephalopathy: Neurological abnormality is diagnosed in CPSS. The severity depends on the type of anatomical defect causing shunt formation.
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Other complications include heart failure, membranoproliferative glomerulopathy, hypoglycemia, pancreatitis, hyperandrogenism, rectal or vaginal bleeding, and autoimmune diseases.
Conclusion
Congenital portosystemic shunt or liver shunt bypasses the liver by the body’s circulatory system. The CPSS is rare in humans and can often be associated with congenital disabilities. The symptoms manifest during the neonatal or early infancy stage. Most shunts resolve their own, but few persist and cause complications.
