Ultrasound images Neonatal cholestasis and biliary atresia

Neonatal hepatitis and biliary atresia are the most common causes of neonatal cholestasis, presenting around the age of 4 weeks with neonatal jaundice, dark urine and pale stools. Early diagnosis of biliary atresia and differentiation from hepatitis and other causes of neonatal cholestasis is crucial to successful treatment. The aetiology of biliary atresia remains unclear but progressive inflammation,
destruction and fibrosis of the biliary tree occurs, resulting in obliteration of all or part of the bile ducts and gallbladder, with the subsequent development of biliary cirrhosis.

The ultrasonic features of neonatal hepatitis and biliary atresia overlap. The gallbladder is generally small and thick-walled or absent in biliary atresia, but may occasionally appear normal, whereas in hepatitis the gallbladder, although often normal in
size, may be difficult to visualize. The presence or absence of a gallbladder is not a reliable sign of biliary atresia. In cases of biliary atresia where only the hepatic duct is atretic (that is, with a normal gallbladder and common duct), the gallbladder can
appear normal in size and contract postprandially. The liver may appear normal but in more severe cases the liver parenchyma shows increased echogenicity due to developing cirrhosis. The intraand extrahepatic biliary tree is not dilated, although occasionally small choledochal cysts or
intrahepatic bile lakes may be seen close to the porta hepatis in infants with biliary atresia.
Approximately 10–20% of infants with biliary atresia have associated congenital abnormalities, including choledochal cyst, situs inversus, polysplenia, preduodenal portal vein and interruption of the inferior vena cava (IVC) with azygous continuation, all of which may be detected on sonography. The main role of sonography is to exclude other less frequent causes of neonatal cholestasis such as a
congenital choledochal cyst and obstruction to the common bile duct due to bile inspissation where
biliary tract dilatation will be noted. The diameter of the normal common bile duct should not be greater than 2 mm in the infant up to 1 year old (or 4 mm in children up to 10 years of age). Liver biopsy and radioisotope studies are used to differentiate biliary atresia from neonatal hepatitis.
Excretion of radionuclide from the liver into the duodenum excludes biliary atresia although a lack of excretion into the duodenum may be seen in both atresia and severe neonatal hepatitis. In these cases laparotomy with intraoperative cholangiogram will be necessary to reach a final diagnosis, although in a few centres MR cholangiography and/or endoscopic retrograde cholangiopancreatography (ERCP) have been used to identify a patent biliary tree and thus exclude the diagnosis of biliary atresia.
Biliary atresia is usually treatable by early surgery, provided the diagnosis is made before the age of 8 weeks, at which time irreversible biliary cirrhosis may have developed. Liver transplant may eventually be required, particularly in those presenting late
with established biliary cirrhosis.

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