Biliary Atresia - USG Reporting & Findings

Note: The query appears to be "biliary atresia" (not "biliary ascleresis" - there is no recognized condition by that name). If you meant a different condition, please clarify.

Background

Sonographic Signs of Biliary Atresia

1. Triangular Cord Sign (Most Specific)

• Defined as a triangular or tubular echogenic density (fibrous ductal remnant) located cranial to the portal vein bifurcation, at the anterior aspect of the right portal vein at its bifurcation
• Represents the fibrotic obliterated remnant of the extrahepatic bile ducts
• Positive criterion: thickness of echogenic anterior wall of right portal vein (EARPV) >3-4 mm on longitudinal scan

• Sensitivity: 74% (95% CI: 0.61-0.84)
• Specificity: 97% (95% CI: 0.95-0.99) - highly specific
• Accuracy: ~93-94%
• PPV: ~94%, NPV: ~94%

2. Gallbladder Abnormalities

• Sensitivity: 85% (95% CI: 0.76-0.91)
• Specificity: 92% (95% CI: 0.81-0.97)

Note: In ~10% of BA patients, the distal biliary tract is patent and a gallbladder may be seen - so presence of gallbladder does NOT exclude BA.

3. Absence of Common Bile Duct

• Non-visualization of the CBD is a supporting finding
• Less valuable than triangular cord sign and gallbladder findings

4. No Biliary Dilatation

• Critical negative finding - intrahepatic bile ducts are NEVER dilated in BA
• This differentiates BA from choledochal malformation and other obstructive causes
• Absence of biliary dilatation or sludge in a jaundiced infant should prompt suspicion for BA

5. Hepatic Artery Enlargement

• Hepatic artery diameter >2 mm at the porta hepatis is a supporting sign
• Less specific but useful adjunct

6. Liver Parenchyma Changes

• Often inhomogeneous with markedly increased periportal echoes due to fibrosis
• Progressive liver enlargement
• Signs of portal hypertension in advanced/late cases: splenomegaly, ascites, reversal of portal venous flow

Combined Diagnostic Performance

• Sensitivity: 95% (95% CI: 0.70-0.99)
• Specificity: 89% (95% CI: 0.79-0.94)

Standard USG Reporting Checklist for Suspected Biliary Atresia

1. Liver - size, echogenicity, parenchymal texture, periportal echogenicity
2. Porta hepatis / Triangular cord sign - presence/absence, thickness of EARPV (measure in mm)
3. Gallbladder - present/absent; if present: length, wall characteristics (smooth vs. irregular), mucosal lining, response to feeding (motility)
4. Common bile duct - visualized/not visualized; if seen, measure diameter
5. Intrahepatic bile ducts - dilated or not (dilatation argues against BA)
6. Hepatic artery - diameter at porta hepatis (>2 mm supports BA)
7. Portal vein - direction of flow, any thrombosis
8. Spleen - size (splenomegaly suggests portal hypertension or polysplenia syndrome)
9. Associated anomalies - polysplenia, preduodenal portal vein, situs, IVC

Differential Diagnosis on USG

Additional Investigations After USG

• Hepatobiliary scintigraphy (99mTc-HIDA/DISIDA): High sensitivity but false-positive rate >20%; non-excretion of radionuclide into bowel supports BA but not specific
• MRCP: 82% accurate, 90% sensitive, 77% specific; useful for anatomy
• Liver biopsy: Inflammatory cells + fibrotic parenchyma + bile neoductal structures = definitive diagnosis
• Intraoperative cholangiography: Definitive diagnosis; required to define surgical anatomy for Kasai portoenterostomy

Key clinical point: Kasai portoenterostomy performed before 8 weeks of age gives the best outcomes - approximately half of patients reach adolescence without needing transplant. Early USG diagnosis is therefore time-critical.