Introduction
There are many causes of neonatal jaundice.
Most cholestatic conditions can be classified as either obstructive or hepatocellular in origin.
Biliary atresia (BA) accounts for more than 90% of obstructive cholestasis cases.
Hepatocellular cholestasis results from the impairment of bile formation and indicates defective functioning of most or all hepatocytes.
Idiopathic neonatal hepatitis accounts for the majority of cases of hepatocellular cholestasis.
Discrimination between these two entities is very important,
since they require completely different approaches towards treatment – medical treatment for hepatitis and surgery for biliaryatresia.
Among non-invasive imaging tools,
it is well known that Ultrasound (US) has the highest diagnostic accuracy,
which makes it possible to avoid unnecessary invasive procedures in many cases.
Biliary Atresia
BA appears after birth with jaundice and is characterized by portal tract inflammation,
a small cell infiltrate and bile duct plugging and proliferation.
This fibrosclerosing and obliteration of the biliary ducts may affect different segments of the extrahepatic biliary tract,
resulting in a variety of anatomical subtypes.
Kasai classification (Fig. 1) is used to describe the three main anatomical types of BA.
type I: obliteration of common bile duct (patent cystic and common hepatic duct).
type II:
IIa: obliteration of common hepatic duct (patent cystic and common bile duct),
sometimes with a cyst at hilum hence termed cystic BA.
IIb: obliteration of common hepatic duct,
cystic and common bile duct.
type III: obliteration of left and right main hepatic ducts at the level of portahepatis (most common,
90%).
Fig. 1: Kasai classification. CBD – common bile duct, CHD –common hepatic duct, GB – gallbladder.
References: Ramachandran et al. Indian Pediatr 2015;52: 871-879
In later stages of the disease,
bridging fibrosis gives way to features of overt biliary cirrhosis.
Diagnosis is usually performed by ultrasound,
hepatobiliary scintigraphy and liver biopsy and confirmed by surgical colangiography.
Primary treatment of BA is the hepato-portoenterostomy (Kasai procedure) to re-establish bile flow,
delaying fibrosis and biliary cirrhosis.
Liver transplantation,
however,
becomes the only therapeutic option in patients with long-standing BA.
BA represents the most common indication for pediatric liver transplantation,
accounting for at least 50% of all pediatric cases.
Ultrasound and Color Doppler
US and Color Doppler are the most commonly used non-invasive means of radiologic assessment for the preoperative diagnosis of BA.
The US and Color Doppler parameters used for the preoperative diagnosis of BA are:
- Triangular Cord Sign
- Abnormal Gallbladder
- Absence of Common Bile Duct
- Hepatic Subcapsular Flow
- Size of Hepatic Artery and Portal Vein
- Hepatomegaly and Splenomegaly
