A nuclear test, called an HIDA (hepatobiliary iminodiacetic acid) scan , determines the flow of bile. In this scan, a radioactive dye is injected into the infant’s vein. The dye acts like bilirubin. If the baby has biliary atresia, the liver will take up the dye but it will not be able to flow through the damaged biliary system into the small intestine. Rather, the tracer enters the circulation and collects in the bladder.