[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Embryology](https://durgical.com/en/embryology/) › [Digestive system](https://durgical.com/en/embryology/#a-digestive) › Biliary atresia [Embryology](https://durgical.com/en/embryology/) · [Digestive system](https://durgical.com/en/embryology/#a-digestive) # Biliary atresia - Malformation The ducts that carry bile out of the liver inflame and close in the first weeks of life: jaundice that does not fade and very pale stools. Updated 2026-11-01 **See it in 3D:** [Common bile duct](https://durgical.com/en/anatomy/bile-duct/) · [Common hepatic duct](https://durgical.com/en/anatomy/common-hepatic-duct/) · [Cystic duct](https://durgical.com/en/anatomy/cystic-duct/) · [Gallbladder](https://durgical.com/en/anatomy/gallbladder/) · [Liver](https://durgical.com/en/anatomy/liver/) · [Portal vein](https://durgical.com/en/anatomy/hepatic-portal-vein/) ## Key points - Jaundice with raised direct (conjugated) bilirubin beyond two to three weeks of life. - Acholic (pale, clay-coloured) stools, dark urine and hepatomegaly. - Ultrasound: triangular cord sign at the porta hepatis; small or absent gallbladder. - Hepatobiliary scan with no tracer reaching the bowel; liver biopsy shows bile ductular proliferation. - Kasai portoenterostomy, ideally before 60 days of life; many children later need a transplant. - Syndromic form (about 10 %): polysplenia, situs inversus, preduodenal portal vein, malrotation and heart defects. ## What it is It is a progressive fibro-obliterative cholangiopathy of the extrahepatic and later intrahepatic bile ducts of infants that blocks bile outflow. It is not simply a failure of recanalization: current thinking is a developmental vulnerability, sometimes with laterality defects, followed by an inflammatory or viral injury after birth. Without early surgery it leads to cirrhosis, and it is a leading reason for liver transplantation in children. ## Embryological cause - Isolated form, the most common: the biliary tree forms but undergoes progressive inflammatory obliteration around birth. - Two-hit model: a developmental vulnerability (abnormal ductal plate remodelling, possible ciliopathy) plus a postnatal immune or viral injury (CMV in a subgroup). - Syndromic form: an early developmental defect tied to laterality, with a splenic malformation. - The obliterated duct remains as a fibrous cord at the porta hepatis. ## How it presents - Jaundice that appears or persists after the second week in an infant who at first looks well. - Increasingly pale stools and dark urine. - Firm hepatomegaly; later splenomegaly, ascites and poor growth from cirrhosis. - Bleeding from vitamin K deficiency due to fat malabsorption. - Associations: polysplenia, heterotaxy, preduodenal portal vein, interrupted inferior vena cava and malrotation. ## Diagnosis - Raised direct bilirubin; prolonged infant jaundice is investigated with fractionated bilirubin. - Fasting ultrasound: triangular cord and a small or absent gallbladder. - Hepatobiliary scan: no excretion into the bowel; if tracer reaches the bowel, biliary atresia is ruled out. - Liver biopsy and intraoperative cholangiography confirm the diagnosis. ## Memory aid A yellow baby with chalk-white stools: the bile is locked in, and every week that passes counts against the liver. ## Test yourself Think of the answer, then tap the question to see it. ## Which bilirubin fraction is raised in biliary atresia? Direct or conjugated bilirubin, because the liver conjugates it but cannot excrete it through the bile ducts. ## Which ultrasound sign is characteristic? The triangular cord: an echogenic fibrous remnant at the porta hepatis. ## Why does early surgery matter? Because the Kasai portoenterostomy works best before 60 days; after that fibrosis progresses toward cirrhosis. ## Which anomalies are associated with the syndromic form? Polysplenia, situs inversus, preduodenal portal vein, interrupted inferior vena cava, malrotation and heart defects. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/embryology/biliary-atresia/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Common bile duct](https://durgical.com/en/anatomy/bile-duct/) - [Common hepatic duct](https://durgical.com/en/anatomy/common-hepatic-duct/) - [Cystic duct](https://durgical.com/en/anatomy/cystic-duct/) - [Gallbladder](https://durgical.com/en/anatomy/gallbladder/) - [Liver](https://durgical.com/en/anatomy/liver/) - [Portal vein](https://durgical.com/en/anatomy/hepatic-portal-vein/) ## Related - [Liver, gallbladder and pancreas](https://durgical.com/en/embryology/liver-gallbladder-and-pancreas/) - [Mesenteries, the omental bursa and the spleen](https://durgical.com/en/embryology/mesenteries-the-omental-bursa-and-the-spleen/) - [Malrotation and midgut volvulus](https://durgical.com/en/embryology/malrotation-and-midgut-volvulus/) - [TORCH infections: what each agent does to the embryo and fetus](https://durgical.com/en/embryology/torch-infections-what-each-agent-does-to-the-embryo-and-fetus/) ## Related conditions - [Neonatal jaundice](https://durgical.com/en/conditions/neonatal-jaundice/) - [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/) - [Portal hypertension](https://durgical.com/en/conditions/portal-hypertension/) [← All of embryology](https://durgical.com/en/embryology/) Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given. Sources: [Biliary Atresia](https://www.ncbi.nlm.nih.gov/books/NBK537262/) (StatPearls Publishing (NCBI Bookshelf), 2026); [Biliary atresia](https://medlineplus.gov/ency/article/001145.htm) (MedlinePlus, U.S. National Library of Medicine, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/embryology/biliary-atresia/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/embryology/biliary-atresia/