Sonographic diagnosis of biliary ascariasis.

In an 11.5-year-old boy with obstructive jaundice sonography revealed a worm-like structure within the dilated biliary tree. Cross-section showed a bull's eye configuration, whereas longitudinal planes demonstrated an echogenic strip with a central longitudinal anechogenic tube. Diagnosis of ascariasis was established by identification of ascarid eggs in the stool. After anthelminthic treatment several ascarid worms were excreted with the stool.