Biliary Atresia is a condition in babies where the bile ducts, which help carry waste from the liver, are blocked. This study aims to learn more about what causes biliary atresia and how it progresses. It involves collecting information, genetic material (like DNA), and body fluids from children with this condition. Researchers want to find out if genes, immune system problems, or other factors contribute to the disease. They also want to understand how the disease affects children as they get older, especially those who haven't had a liver transplant. The study is conducted by the Childhood Liver Disease Research Network, funded by a national health institute.

• Participants must be older than 6 months and up to 20 years old, with a confirmed biliary atresia diagnosis.
• The study requires consent from parents or guardians, or from the participant if they are 18 or older.
• Those already in a related study or unable to attend visits cannot participate.