eMedicine Specialties > Radiology > Pediatrics

Biliary Atresia

Author: Katherine Zukotynski, MD, Staff Physician, Department of Medical Imaging, University of Toronto
Coauthor(s): Paul S Babyn, MD, Associate Professor, Department of Medical Imaging, University of Toronto; Radiologist-in-Chief, Department of Diagnostic Imaging, The Hospital for Sick Children
Contributor Information and Disclosures

Updated: Jun 9, 2006

Introduction

Background

Biliary atresia is a condition in which the normal extrahepatic biliary system is disrupted. Progressive damage of extrahepatic and intrahepatic bile ducts secondary to inflammation may occur, leading to fibrosis, biliary cirrhosis, and eventual liver failure.

Biliary atresia affects approximately 1 in 10,000-15,000 births and occurs in 2 distinct forms: fetal-embryonic and postnatal.

The fetal-embryonic form appears in the first 2 weeks of life and accounts for 10-35% of all cases. In this form, the bile ducts are discontinuous at birth, and 10-20% of affected neonates have associated congenital defects, including situs inversus, polysplenia, malrotation, intestinal atresia, and cardiac anomalies, among others. The postnatal form of biliary atresia accounts for the remaining 65-90% cases. This form is typically found in neonates and infants aged 2-8 weeks. Progressive inflammation and obliteration of the extrahepatic bile ducts occur after birth. This form is not associated with congenital anomalies, and infants may have a short jaundice-free interval.

In the past, biliary atresia was classified according to whether the disease could or could not be surgically corrected. As Image 1 shows, in the correctable group, the proximal common hepatic duct is patent, allowing for primary anastomosis of the bile duct to the bowel. Now, resection of the fibrous bile duct remnant may be done, followed by a Roux-en-Y anastomosis of the bowel to the bed of porta hepatis, according to the Kasai portoenterostomy procedure.

The Kasai classification system is widely used and divides cases of biliary atresia according to their location and degree of pathology. As shown in Image 2, 3 main types of biliary atresia are defined. In type I, the common bile duct is obliterated while the proximal bile ducts are patent. In type II, atresia of the hepatic duct is seen, with cystic bile ducts found at the porta hepatis. In type IIa, the cystic and common bile ducts are patent, whereas in type IIb, the cystic, common bile duct and hepatic ducts are all obliterated. Type III atresia refers to discontinuity of both right and left hepatic ducts to the level of the porta hepatis. Unfortunately, type III biliary atresia is common, accounting for >90% of cases.

Pathophysiology

The pathogenesis of biliary atresia is poorly understood. Although several mechanisms are implicated, no single etiologic factor is identified. Association with congenital anomalies in some infants suggests genetic factors. Infection with cytomegalovirus, group C rotavirus, and reovirus type 3 have been implicated in certain cases. Cholestasis almost certainly contributes to ongoing hepatocellular and biliary damage in infants with the disorder.

Histologic findings on liver biopsy typically include acute on chronic inflammatory change with obstruction, fibrosis, and the proliferation of ductal and glandular elements. Findings may not be definitive early in the course of the disease, and repeat biopsy may be required to reach a definitive diagnosis. Image 3 depicts the histologic findings associated with biliary atresia.

Frequency

United States

The overall incidence is 1 in 10,000-15,000 live births.

International

The incidence is higher in the Asian population than in other groups.

Mortality/Morbidity

Although the exact numbers may vary, the overall survival rate of children after surgical treatment for biliary atresia is approximately 60% at 5 years and 35% at 10 years.

Race

In the United States, African American infants are more commonly affected than white infants.

Sex

A slight female predominance is noted.

Presentation

Clinical manifestations of biliary atresia are nonspecific. Infants were often born at full term, they appear healthy despite having jaundice, and they have a normal gestational history and initial weight gain. Their stools often become progressively acholic during the first weeks of life. Although hepatosplenomegaly may appear early, chronic hepatic failure is rare at the time of diagnosis. Associated congenital anomalies may or may not be present.

No single biochemical marker can be used to distinguish biliary atresia from other causes of neonatal cholestasis. Conjugated (direct) hyperbilirubinemia is defined by a serum conjugated bilirubin concentration > 2 mg/dL (34.2 mmol/mL) or 15% of the total bilirubin level. At the time of diagnosis, the total serum bilirubin level is typically 6-12 mg/dL with 50-80% conjugated. The patient's prothrombin time and levels of serum aminotransferase, gamma-glutamyl transferase (GGTP), and alkaline phosphatase may be elevated.

Neonatal jaundice may be due to a variety of causes, including hemolysis, sepsis, and metabolic disease, among others. When jaundice persists longer than 14 days, biliary atresia and idiopathic neonatal hepatitis must be considered. Together, these conditions cause more than 90% of all cases of neonatal obstructive cholestasis.

Early differentiation of extrahepatic biliary atresia from medical causes of hepatic dysfunction is important because earlier surgical intervention is directly associated with better outcomes.

Preferred Examination

Several imaging modalities have been used in the diagnosis of biliary atresia. Although some findings are highly suggestive of the disease, none is pathognomonic, and reliance on more than one test is common. Ultrasonography is the best initial investigation in patients with suspected biliary atresia, and liver biopsy can be used to confirm the diagnosis.

If the diagnosis remains elusive after ultrasonography, hepatobiliary scintigraphy, magnetic resonance (MR) cholangiography, and/or liver biopsy followed by surgical or percutaneous cholangiography is recommended. Alternative procedures include duodenal intubation and endoscopic retrograde cholangiopancreatography, which are generally not considered in infants.

Cholangiography

In general, if clinical concern persists after ultrasonography and hepatobiliary scintigraphy are performed, exploratory laparotomy with surgical cholangiography is recommended. This is typically done by injecting contrast material through the gallbladder. If no communication is seen between the biliary tree and the gastrointestinal tract, biliary atresia is diagnosed.

Percutaneous transhepatic cholangiography is rarely performed to diagnose biliary atresia. It is technically challenging, and the results are definitive only if a normal intrahepatic and extrahepatic biliary system is seen.

Sonography-guided percutaneous cholecystocholangiography is a new technique in which radiographic contrast material is injected into the gallbladder under sonographic guidance and the extrahepatic biliary system is viewed by using fluoroscopy. Although invasive, the technique has distinct advantages in that it is relatively easy to perform and that it does not require general anesthesia.

Endoscopic retrograde cholangiopancreatography allows direct visualization of the extrahepatic biliary tree with the injection of radiologic contrast agent into the extrahepatic biliary system through the papilla of Vater. It is a rarely used invasive technique, and it requires the use of general anesthetic, substantial expertise, and the availability of sufficiently small endoscopes. This technique can show obstruction in the common bile duct and enables visualization of the extrahepatic biliary system distal to the common hepatic duct and the extrahepatic biliary system with bile lakes at the porta hepatis.

Duodenal intubation

Duodenal intubation is not commonly used in diagnosing biliary atresia because it is cumbersome and because strict criteria for the technique are not defined. To perform this study, a nasogastric tube is placed in the distal duodenum. The absence of bilirubin or bile acids in aspirated fluid suggests obstruction. Positive predictive values are as high as 92%, with sensitivity and specificity higher than 90%.

The detection of radioactive tracer in aspirated duodenal fluid after hepatobiliary scintigraphy was studied. The utility of the test is not well defined.

Liver biopsy

Percutaneous liver biopsy is useful in evaluating neonatal cholestasis. Histologic findings, including bile-duct proliferation and obstruction, may not be definitive in neonates younger than 2 weeks. Results of repeat biopsy at 2-week intervals confirm the diagnosis in as many as 95% of patients. Laparotomy and intraoperative cholangiography are recommended when the diagnosis is uncertain.

Differential Diagnoses

Other Problems to Be Considered

Alagille syndrome
Caroli disease
Cholestasis
Cystic fibrosis
Cytomegalovirus infection
Galactose-1-phosphate uridyltransferase deficiency (galactosemia)
Hemochromatosis, neonatal
Herpes simplex virus infection
Lipid-storage disorders
Rubella
Syphilis
Toxoplasmosis
Alpha-1-anti-trypsin deficiency
Byler disease
Choledochal cyst
Idiopathic neonatal hepatitis
Inborn errors of bile acid synthesis
Nonsyndromic intrahepatic bile duct hypoplasia
Total parenteral nutrition (TPN)–associated cholestasis
Viral infections (eg, toxoplasmosis, rubella, cytomegaloviral infection, others)

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