Biliary atresia

Biliary atresia is a congenital biliary disorder that is characterized by an absence or severe deficiency of the extrahepatic biliary tree. It is one of the most common causes of neonatal cholestasis, often causing cirrhosis immediately and leading to death and accounts for over half of children who undergo liver transplantation. 

Epidemiology

It is thought to affect 1 in 10,000-15,000 newborn infants. There is a recognized male predilection.

Associations

There are two different forms of biliary atresia:

• non-syndromic (~90%): isolated atresia of bile ducts

• syndromic (~10%): associated with various congenital anomalies such as polysplenia, asplenia, heterotaxy syndrome, intestinal malrotation, and interrupted IVC

Clinical presentation

It presents within the first three months of life. Infants with biliary atresia may appear normal and healthy at birth. Most often, symptoms develop between two weeks to two months of life, and may include:

• jaundice (conjugated hyperbilirubinemia)

• dark yellow or brown urine

• pale or clay-colored (acholic) stools

• hepatomegaly

Pathology

Etiology

Although typically thought to result from an idiopathic destructive inflammatory process that leads to fibrotic remnants at porta hepatis, the disease may be secondary to viral infections or autoimmune-induced injury in some cases.

Classification

The Kasai classification is used to classify the three main anatomical types of biliary atresia.

Radiographic features

Prompt diagnosis ensures early treatment and results in improved prognosis.

Ultrasound

• echogenic fibrous tissue anterior to the portal vein: triangular cord sign ⁵

  • represents ductal remnant of extrahepatic bile duct

• hepatic artery changes

  • larger hepatic arterial caliber ²

  • subcapsular hepatic arterial flow on Doppler

  • right proximal hepatic artery diameter >1.5 mm

  • hepatic artery to portal vein diameter ratio >0.45

• gallbladder ghost triad ⁴

  • atretic gallbladder, length less than 19 mm

  • irregular or lobular contour 

  • lack of smooth/complete echogenic mucosal lining with an indistinct wall

• gallbladder contraction index decreased for the age (length to width ratio >5.2)

Nuclear medicine

Hepatobiliary (HIDA) scan

Tc-99m diosgenin (DISIDA) and mebrofenin (BRIDA) have the highest hepatic extraction rate and shortest transit time of hepatobiliary radiotracers. Cases of biliary atresia typically demonstrate relatively good hepatic uptake with no evidence of excretion into the bowel at 24 hours. Pretreatment with phenobarbital (5 mg/kg/day for 5 days) to increase biliary secretion by stimulating hepatic enzymes is frequently helpful to minimize the possibility of a false-positive study in a patient with a patent biliary system but poor excretion.

Treatment and prognosis

It is important to diagnose biliary atresia early since a Kasai portoenterostomy done within the initial two months of life has a very good prognosis.

Management options include:

• Kasai portoenterostomy: the surgery involves exposing the porta hepatis (the area of the liver from which bile should drain) by radical excision of all bile duct tissue up to the liver capsule and attaching a Roux-en-Y loop of jejunum to the exposed liver capsule above the bifurcation of the portal vein creating a portoenterostomy ⁷

• liver transplantation

Complications

• portal hypertension ³

• cirrhosis ⁸

Differential diagnosis

General imaging differential considerations include:

• neonatal hepatitis

• Alagille syndrome

• Caroli disease

• bile plug syndrome

• lipid storage disorders