Biliary atresia classification
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Biliary atresia classification On the Web
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Biliary atresia can be classified into several subtypes, since it does not arise from a specific cause. As such, it is broadly classified according to syndromic and non-syndromic expression. Biliary atresia can be classified by:
Biliary Atresia Splenic Malformation Syndrome (BASM)
In this type, malformation occurs early in embryogenesis also giving rise to other anomalies. Biliary atresia is associated with polysplenia, vascular anomalies including a pre-duodenal portal vein, interrupted vena cava, azygous continuation, cardiac malformation, malrotation, and situs inversus. Maternal diabetes may be associated, and there is a female predominance.
Cystic Biliary Atresia
In this type, the biliary system gets destroyed with subsequent cystic dilatation. The incidence is reported to be around 10%, and it carries a better prognosis.
Cytomegalovirus (CMV) IgM Positive Biliary Atresia
This type is associated with CMV infections, and present with higher bilirubin and aspartate aminotransferase (AST) levels and more inflammatory infiltrates in the extrahepatic biliary ducts on histology. It represents about 10% of the cases, and has the worst prognosis. Most of these patients are non-Whites.
Isolated Biliary Atresia
This represents the largest group, but the etiology is unknown.
Morphological classification is based on the level at which the biliary lumen is obliterated. The Japanese Association Of Pediatric Surgeons has classified it as:
- Type I: Obliteration of the common bile duct
- Type II a: Obliteration of the common hepatic duct
- Type II b: Obliteration of the common bile duct, hepatic duct, cystic duct with no abnormality of the gallbladder, and cystic dilatation at the porta hepatis
- Type III: Obliteration of the most proximal part of the common bile duct, hepatic duct, and cystic duct with no anastomosable ducts at the porta hepatis (Most common). 
- Siddiqui AI, Ahmad T. Biliary Atresia. [Updated 2021 Jul 25]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537262/