How is biliary atresia differentiated from neonatal hepatitis on hepatobiliary scintigraphy?
In both disorders, the bilirubin level is extremely high, making adequate visualization of radiotracer activity entering into the small bowel difficult to assess. During the initial hour of imaging, radiotracer activity is usually seen in the liver with persistent cardiac blood pool activity. Delayed imaging at 4 hours and sometimes 24 hours is required to determine whether any radiotracer activity is observed entering into the bowel. If any radiotracer does enter the bowel, biliary atresia can be excluded, and the diagnosis of neonatal hepatitis can be made. Absence of radiotracer activity in the small bowel can still be related to either disorder, however, because if insufficient radiotracer is sent into the biliary system by the liver, it is impossible to evaluate for potential complete biliary obstruction.