IMAGING IN BILIARY ATRESIA

biliary atresia
a condition in which there is aplasia or obliteration of some or all of the extrahepatic biliary tree: the gallbladder may or may not be involved. It presents in the neonate or young infant with clinical findings of obstructive jaundice and conjugated hyperbilirubinaemia. If undiagnosed or unrelieved progressive biliary cirrhosis will develop. The prognosis is inversely related to the age at which surgery is undertaken and the degree of liver damage. The aetiology is unknown but some consider it to be due to an inflammatory process which leads to progressive obliteration of the bile ducts in the perinatal period.

At ultrasound examination, which should be done following a 4-hour fast, before the onset of cirrhosis, the liver is normal. There is no intrahepatic bile duct dilatation. The gallbladder is not usually seen but if identified it may be spherical. The extrahepatic biliary tree is not seen. A normal ultrasound examination does not exclude the diagnosis. Hepatobiliary scintigraphy using a Tc99m-labelled iminodiacetic acid product (e.g. HIDA) typically demonstrates good hepatic uptake of tracer, with progressive accumulation within the liver but no evidence of excretion into the extrahepatic bile ducts or into bowel. Premedication with phenobarbitone for 5 days prior to the study is recommended to ensure maximal hepatic enzyme function should there be some impairment of liver function. The absence of bowel activity at 24 hours is generally taken to be an indication for liver biopsy and/or operative cholangiography. Findings in neonatal hepatitis include poor hepatocellular uptake of tracer, delayed excretion into bowel and occasionally non-excretion as in biliary atresia.

Treatment is surgical and involves anastomosing an intrahepatic bile duct (usually in segment III) to a loop of jejunum to bypass the extrahepatic obstruction (Kasai procedure). Complications include sepsis and anastamotic stricture. The procedure should be performed as early as possible after diagnosis to avoid complications related to cirrhosis and portal hypertension.