Biliary Atresia

Definition

Epidemiology

• Incidence: 1 in 8,000–18,000 live births in the USA
• Accounts for ~one-third of cases of neonatal cholestatic jaundice
• Slight female predominance
• Not inherited; discordant in dizygotic and monozygotic twins
• Non-Hispanic Black infants may carry higher risk
• Not associated with seasonality or time-space clustering

Classification / Pathogenesis

• Viral injury: CMV (56% of BA patients had elevated IFN-γ liver T-cells in response to CMV), rotavirus group C, reovirus type 3, EBV
• Immune dysregulation: autoimmunity, dysregulated T-regulatory cell function, coordinated activation of lymphocyte differentiation genes
• Genetic susceptibility: GPC1 (glypican-1, regulates Hedgehog signaling), ADD3, XPNPEP1 at locus 10q24.2; cfc1 gene mutations in biliary atresia-splenic malformation syndrome
• Toxin exposure: plant isoflavonoid ingestion linked to BA in livestock and zebrafish models
• Maternal microchimerism: expression of maternal antigens may trigger autoimmune bile duct destruction

Morphology / Pathology

• Inflammation and fibrosing stricture of the hepatic or common bile ducts
• Periductular inflammation may extend into intrahepatic ducts → progressive destruction
• Bile duct proliferation at portal plates (seen on trichrome staining) — a nonspecific but characteristic marker
• Intrahepatic bile ducts are NEVER dilated in biliary atresia (key distinguishing feature)
• If unrecognized/untreated: cirrhosis within 3–6 months of birth

• ~10%: distal duct is patent; gallbladder may be visible — proximal ducts still atretic
• ~90%: obstruction at or above the porta hepatis — no patent bile ducts amenable to anastomosis
• When limited to common duct or hepatic ducts with patent intrahepatic branches → surgically correctable

Clinical Presentation

• Jaundice at birth or shortly thereafter (easily confused with physiologic neonatal jaundice, causing diagnostic delay)
• Acholic (pale gray) stools — hallmark of obstructed bile flow; stools may initially appear normal, becoming acholic with disease progression
• Dark urine (conjugated hyperbilirubinemia)
• Progressive failure to thrive
• If untreated: portal hypertension → splenomegaly, esophageal varices, ascites
• ~25% have coincidental malformations (polysplenia syndrome: intestinal malrotation, preduodenal portal vein, azygous continuation of IVC)

Diagnosis

1. Serum bilirubin fractionation → predominantly conjugated (direct) hyperbilirubinemia
2. Liver function tests: elevated GGT, alkaline phosphatase, transaminases
3. TORCH titers / viral hepatitis serologies (to exclude infectious causes)
4. Abdominal ultrasound:
   • Absence of gallbladder — highly suggestive
   • Gallbladder presence does NOT exclude BA (present in ~10%)
   • No dilated intrahepatic ducts (helps distinguish from choledochal cyst)
5. Hepatobiliary scintigraphy (Tc-99m DISIDA/HIDA scan) after phenobarbital pretreatment:
   • Radionuclide in intestine = biliary patency → BA excluded
   • No excretion into intestine → consistent with BA
6. Liver biopsy: portal fibrosis, bile duct proliferation, bile plugs in ducts
7. Intraoperative cholangiogram — definitive; confirms obstruction pattern before Kasai procedure

Surgical Treatment — The Kasai Procedure

• The fibrous remnant of the extrahepatic biliary tree is excised at the level of the porta hepatis
• A Roux-en-Y loop of jejunum is anastomosed directly to the transected porta hepatis to drain bile
• Timing is critical: best outcomes when performed before 60 days of age; outcomes deteriorate significantly after 90 days

• ~50% of patients who undergo timely Kasai will achieve adequate bile drainage
• Even with successful drainage, many develop progressive intrahepatic disease
• Ascending cholangitis is a major post-operative complication (treated with antibiotics; some centers use prophylactic antibiotics)
• Overall: ~30–50% survive to age 10 without liver transplantation after successful Kasai

Liver Transplantation

• Remains the definitive treatment for failed Kasai or end-stage liver disease
• Biliary atresia is the leading indication for pediatric liver transplantation (~50% of all pediatric transplants)
• 5- and 10-year post-transplant survival rates are excellent (>80%)

Key Points Summary