Biliary atresia

The term “atresia” refers to the congenital absence or abnormal narrowing of a body opening. Therefore, we can deduce that the name biliary atresia refers to a congenital or acquired absence, discontinuity or obliteration of the extrahepatic bile ducts.

Approximately 1 in 17,000 children in the UK have biliary atresia. Females are more affected than males. In Asia, the incidence is much higher with 1 in 5,000 reported to have this condition.

It is the most common reason for liver transplantation in children. It is a rare, but life-threatening condition that is fatal if not intervened.

Pathophysiology

The exact underlying cause of biliary atresia is not quite known, however, several risk factors have been suggested:

• Genetics - geographical distribution suggests that there is a genetic component to the disease. Genes implanted may be CFC1, ADD3, EFEMP1.
• Viral infections - there is a correlation seen between perinatal infection with rotavirus, reovirus type 3 and viral hepatitis viruses.
• Antenatal circulatory defects - damage may occur to the bile ducts when there is reduced flow to the hepatic arterial circulation.
• Biliatresone toxin - this is a toxin found in the Dysphania species of plants. It has been shown to cause damage to cholangiocytes in animal models.
• Embryological defects - as biliary atresia is associated with other congenital anomalies, this suggests that it occurs as a result of insult at a critical time in the development of the foetus.
• Autoimmune dysregulation - autoimmune attack on bile duct epithelia leads to inflammation of the bile ducts.

The factors mentioned above lead to progressive inflammation of the extrahepatic bile ducts. This may be just a single duct, or the entire ductal system. The inflammation may ascend from the extrahepatic ducts to the intrahepatic biliary system. Eventually inflammation leads to fibrosis → cirrhosis. Cirrhosis then causes portal hypertension which has its associated complications. The disease leads to an obstructive jaundice and liver failure.

This damage may occur in-utero or postnatally. If in-utero it presents within the first 2 weeks of life. If it occurs in the postnatal period then it presents within the first 2-8 weeks of life.

⚠️ Risk factors

• Genetic predisposition
• Viral infections
• Dysphania species of plants

😷 Presentation

It usually presents in the first weeks of life with a prolonged jaundice (jaundice lasting longer than 14 days in a term baby or longer than 21 days in a preterm baby).

• Pale/chalky white stools - this is known as an acholic stool. It occurs due to obstructive jaundice that prevents bilirubin from reaching the intestines.
• Dark urine - as the conjugated bilirubin (water-soluble) is excreted through urine.
• Cardiac murmurs - as it is associated with other congenital anomalies.

In infants over 3 months old we may see:

• Hepatosplenomegaly
• Ascites
• Failure to thrive - this is due to the malabsorption of fats.

🔢 Classification

We can use the Ohi classification system to classify the biliary atresia by the anatomical variants that are seen with biliary atresia:

1. Type I - common bile duct atresia. The proximal ducts remain patent.
2. Type II - hepatic ducts and common bile duct atresia.
3. Type III - atresia at the level of porta hepatis (the transverse fissure of the liver which is like the hílum of the liver). This is the most common variant.

We may also classify the disorder based on its presentation too:

• Isolated biliary atresia - the infants first stools are normally pigmented and the child is of average birth weight. It is more common.
• Biliary atresia with congenital anomalies

Biliary atresia with splenic malformation syndrome (BASM)

BASM is a form of biliary atresia associated with polysplenia situs inversus, cardiac malformations, vascular anomalies.

🔍 Investigations

📷

Imaging:

• Hepatic scintigraphy (DISIDA or HIDA scan) - the liver takes up the isotope but there is poor excretion into the bowel. This indicates destruction of the bile ducts.
• 🏆 Operative cholangiography - this is the gold-standard to provide definitive diagnosis. It will indicate abnormal architecture of the biliary tree. It is only used if there is diagnostic uncertainty prior to treatment. It involves injecting an iodinated contrast medium into the gallbladder and biliary tree (under general anaesthesia) to highlight the biliary tree architecture.
• Abdominal ultrasound - may show the triangular cord sign which is a triangular echogenic fibrous remnant of the extrehepatic duct. The common bile duct is not visualised. At the level of the porta hepatis only two structures will be seen - the portal vein and the hepatic artery.

• Liver biopsy - may be done to differentiate biliary atresia from intrahepatic causes of cholestasis.
• Guthrie testing (heel prick test) - to exclude differentials such as cystic fibrosis, sickle cell disease, metabolic disorders, thyroid dysfunction, severe combined immunodeficiency (SCID).

🧰 Management

🧰

Management of biliary atresia:

As mentioned earlier, the condition is fatal if not managed appropriately.

🏆 The definitive management is surgical:

• Kasai procedure (hepatoportoenterostomy) - this involves the excision of the diseases extrahepatic duct and gallbladder. The jejunum is separated from the duodenum and is anastomosed to the porta hepatis. The duodenum is then connected to a more distal portion of the jejunum and the jejunum is reconnected to the bowel at a separate location.
• Co-trimoxazole - is given for the first year after the procedure as prophylaxis against cholangitis infection.
• Ursodeoxycholic acid - is also given to aid bile flow.

Patients often require a liver transplant to fully resolve the condition.

🚨 Management

• Cholangitis - this is the most serious and common complication post-Kasai procedure.
• Portal hypertension
• Progressive liver disease
• Cirrhosis
• Hepatocellular carcinoma