In infant biliary atresia, a rare disease in newborns, patients often die within the first few years without treatment. A striking contrast is found in lampreys, a group of extant jawless vertebrates that go through developmental biliary atresia during metamorphosis. The sea lamprey (Petromyzon marinus) loses the entire biliary tree when their larvae metamorphose into parasitic juveniles. The aductular juveniles feed ferociously and grow exponentially into fecund adults without complications or liver failure that afflict patients with biliary atresia or other forms of cholestasis. The transcriptomic analysis of the sea lamprey livers at different development stages may unravel the mechanism that the sea lamprey goes through developmental biliary atresia.