History and exam
Key diagnostic factors
common
neonatal jaundice
Can be difficult to see in dark-skinned babies and may only be apparent in the sclera. Any baby with jaundice and pale stools or with jaundice persisting beyond 14 days of age should have fractionated bilirubin checked.
Further investigation is indicated if direct or conjugated bilirubin exceeds 17.1 micromoles/L (1 mg/dL).[51]
acholic stool
Stools range in colour from white to a tan or light yellow.
Other diagnostic factors
common
dark urine
In the first weeks of life all urine is clear in a wet nappy. When jaundice is present the nappy will show yellow staining. This sign is often ignored because older children will have yellow staining with urine in a wet nappy.
bruising
Coagulopathy can develop secondary to vitamin K deficiency related to chronic cholestasis. This is more common in children who present late.
uncommon
hepatomegaly
In early stages, hepatomegaly may be mild or absent and liver texture normal. It is not until the disease has progressed significantly that the texture is firm, hard, or nodular.
ascites
Present only after significant liver damage has occurred.
Risk factors
weak
genetic predisposition
Most twin studies show no concordance. However, there is an association with HLA-B12, suggesting a genetic background might be necessary for disease expression.[21][45] Genome-wide association studies have implicated the ADD3, EFEMP1 and ARF6 genes as possible susceptibility factors for biliary atresia.[33][34] Exome sequencing of patients with biliary atresia splenic malformation has revealed mutations in the cilia-associated gene PKD1L1.[35][36][37]
viral infection
environmental or behavioural exposures
Some evidence supports an environmental exposure (e.g., the report of a 5-fold increase in incidence among the French population living in Polynesia compared with their native country).[49]
Studies have identified a plant toxin (biliatresone from Dysphania species plants) that causes biliary atresia in newborn lambs.[25] This toxin has been found to damage cholangiocytes in zebrafish, mouse and human cell culture models, and to activate glutathione antioxidant pathways.[26][27]
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