Overview
Definition:
Biliary atresia (BA) is a progressive fibrosing obliterative process of the extrahepatic bile ducts (and often intrahepatic ducts) in infants, leading to conjugated hyperbilirubinemia and ultimately cirrhosis and liver failure if untreated.
Epidemiology:
It is the most common cause of neonatal cholestasis requiring surgical intervention, occurring in approximately 1 in 10,000 to 1 in 20,000 live births worldwide
There are two main forms: embryonic (intrauterine onset) and perinatal (postnatal onset).
Clinical Significance:
Early diagnosis and surgical intervention (Kasai portoenterostomy) are crucial for improving outcomes
Delays in diagnosis significantly worsen prognosis due to irreversible liver damage
Understanding HIDA scan interpretation and the optimal timing for Kasai are critical for pediatric residents preparing for DNB and NEET SS exams.
Clinical Presentation
Symptoms:
Progressive jaundice, particularly conjugated hyperbilirubinemia, typically presenting after the first week of life
Pale, acholic stools
Dark urine
Poor weight gain and failure to thrive
Hepatomegaly noted on physical examination.
Signs:
Generalized jaundice extending beyond the first 1-2 weeks
Persistent pale stools
Dark urine
Enlarged and firm liver
Splenomegaly may develop later as portal hypertension ensues.
Diagnostic Criteria:
There are no specific diagnostic criteria for biliary atresia per se
Diagnosis is made by excluding other causes of neonatal cholestasis and confirmed by intraoperative cholangiogram and liver biopsy
Key indicators include elevated direct/conjugated bilirubin and abnormal liver function tests, coupled with imaging findings.
Diagnostic Approach
History Taking:
Focus on the onset and progression of jaundice
Characterize stool color (pale vs
normal)
Inquire about urine color
Assess feeding patterns and weight gain
A family history of liver or biliary issues is rare but notable.
Physical Examination:
Assess the degree of jaundice, noting scleral icterus and skin discoloration
Inspect stools for acholic or pale appearance
Palpate the abdomen for hepatomegaly, noting its size, consistency, and smoothness
Check for splenomegaly
Assess for signs of dehydration or poor feeding.
Investigations:
Initial labs include complete blood count (CBC), liver function tests (LFTs) showing elevated total and direct bilirubin, alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT)
AST/ALT may be elevated but are often less dramatically so than ALP/GGT
Prothrombin time (PT) and albumin are usually normal early on
Ultrasound of the abdomen can show small or absent gallbladder, triangular cord sign, and biliary dilatation
Hepatobiliary iminodiacetic acid (HIDA) scan is crucial: absent or minimal intestinal excretion of the radiotracer after 24 hours is highly suggestive of BA
A confirmatory liver biopsy is essential for histopathological diagnosis.
Differential Diagnosis:
Other causes of neonatal cholestasis include: Inspissated bile syndrome, neonatal hepatitis (viral, bacterial, metabolic), alpha-1 antitrypsin deficiency, cystic fibrosis, Alagille syndrome, parenteral nutrition-associated cholestasis, and specific inborn errors of metabolism
Differentiating these relies on a combination of clinical presentation, laboratory findings, imaging, and biopsy.
Management
Initial Management:
The primary goal is prompt diagnosis and surgical intervention
Medical management is supportive while awaiting definitive treatment.
Medical Management:
Supportive care includes nutritional support, often with medium-chain triglyceride (MCT) formula to aid fat absorption
Fat-soluble vitamin supplementation (A, D, E, K) is critical due to malabsorption
Ursodeoxycholic acid (UDCA) may be used to improve bile flow, though its efficacy in BA is debated and it is generally not a substitute for surgery.
Surgical Management:
The gold standard surgical treatment is the Kasai portoenterostomy, a procedure where the fibrous remnant of the extrahepatic bile ducts is excised, and an intestinal Roux-en-Y loop is anastomosed to the porta hepatis to allow bile drainage
This aims to restore bile flow to the intestine
The success of the Kasai procedure is highly dependent on the timing of intervention and the presence of patent intrahepatic bile ducts.
Timing Kasai Procedure:
The optimal timing for the Kasai procedure is critical
Ideally, it should be performed before 6-8 weeks of age, and definitely before 90 days
Studies show significantly better outcomes with surgery performed before 30-45 days of life, characterized by better jaundice clearance, lower rates of cirrhosis, and improved long-term survival
Delays beyond 3 months drastically reduce the chances of success and increase the need for liver transplantation.
Hida Scan Interpretation
Purpose:
The HIDA scan (cholescintigraphy) is a functional imaging test used to evaluate bile flow and detect biliary obstruction
In neonates, it helps differentiate BA from other causes of cholestasis.
Procedure:
A radioactive tracer (e.g., Tc-99m mebrofenin or diisopropyl iminodiacetic acid [IDA]) is injected intravenously
The tracer is taken up by hepatocytes and excreted into bile
Serial images are acquired over several hours.
Interpretation Biliary Atresia:
In suspected biliary atresia, the critical finding is the absence of radiotracer excretion into the duodenum and intestines within 24 hours of injection
Tracer may accumulate in the liver and gallbladder (if patent but obstructed), but does not egress
If there is any visualization of the bowel, BA is less likely, and other diagnoses are favored.
Interpretation Other Cholestasis:
In other forms of neonatal cholestasis, such as neonatal hepatitis or inspissated bile, the HIDA scan typically shows gradual excretion of the tracer into the bowel, indicating patency of the biliary tree and intestine, albeit with slower flow or reduced excretion.
Complications
Early Complications:
Sepsis (especially cholangitis post-Kasai), wound infection, bowel obstruction/adhesions, anastomotic leak, bleeding, and persistent or recurrent jaundice.
Late Complications:
Cholangitis, portal hypertension with its sequelae (esophageal varices, ascites, hypersplenism), nutritional deficiencies, liver cirrhosis, and end-stage liver disease requiring liver transplantation.
Prevention Strategies:
Early diagnosis and prompt surgical intervention are paramount for preventing progression to cirrhosis
Meticulous surgical technique during Kasai portoenterostomy minimizes complications
Postoperative care should include aggressive management of cholangitis with antibiotics and nutritional support to prevent vitamin deficiencies.
Prognosis
Factors Affecting Prognosis:
The most significant factor is the age at which Kasai portoenterostomy is performed
The presence and extent of intrahepatic bile duct involvement, and the patient's overall nutritional status also play a role
Early clearance of jaundice post-Kasai is a good prognostic indicator.
Outcomes:
Without treatment, biliary atresia leads to liver failure and death within the first 2 years of life
With successful Kasai portoenterostomy before 8 weeks of age, approximately 30-50% of infants achieve jaundice-free status and have preserved liver function long-term, avoiding liver transplantation
For those who do not achieve adequate bile drainage, liver transplantation becomes necessary
The long-term prognosis after successful liver transplantation is generally good.
Follow Up:
Lifelong follow-up is required for all patients with biliary atresia, regardless of treatment outcome
This includes monitoring for growth, nutritional status, liver function, and signs of portal hypertension
Regular screening for cholangitis and liver fibrosis is essential
For those who undergo liver transplantation, regular immunological monitoring and management of immunosuppression are vital.
Key Points
Exam Focus:
HIDA scan findings for BA (no bowel excretion)
Optimal timing for Kasai portoenterostomy (ideally <8 weeks, certainly <90 days)
Complications of BA and post-Kasai surgery (cholangitis, portal hypertension)
Differentiating BA from other neonatal cholestasis
Role of liver biopsy.
Clinical Pearls:
Always consider BA in any infant with persistent conjugated hyperbilirubinemia beyond 2 weeks of age
A normal-appearing gallbladder on ultrasound does not rule out BA
The "triangular cord sign" on ultrasound is highly suggestive of BA
A truly acholic stool is a red flag for biliary obstruction
Prompt referral to a pediatric surgeon is essential.
Common Mistakes:
Delaying the HIDA scan or liver biopsy until after the optimal window for Kasai surgery has passed
Misinterpreting HIDA scans, especially if intestinal visualization is equivocal
Underestimating the significance of persistent conjugated hyperbilirubinemia
Not considering BA in the differential diagnosis of neonatal cholestasis
Inadequate nutritional support and vitamin supplementation.