Parasitic infestations of the biliary tract.

Parasitic infestations of the biliary tract are a common cause of biliary obstruction in tropical countries and can lead to such serious complications as cholangitis and cholangiocarcinoma. Endoscopic therapy has helped in the management of biliary complications caused by these parasites. Ascaris lumbricoides organisms, which normally reside in the jejunum, are actively motile and can invade the papilla, thus migrating into the bile duct and causing biliary obstruction. Endoscopic retrograde cholangiopancreatography is a useful diagnostic tool with potential for therapeutic management of biliary ascariasis. Infestation with Clonorchis sinensis organisms can cause such complications as intrahepatic stones, recurrent pyogenic cholangitis, cirrhosis, cholelithiasis, pancreatitis, and cholangiocarcinoma. Opisthorchis viverrini, Opisthorchis felineus, and Dicrocoelium dendriticum are closely related to C. sinensis and can also cause serious biliary complications. Fascioliasis, caused by Fasciola hepatica and F. gigantica, is a zoonotic helminthiasis that can present as acute hepatic or chronic biliary tract infection. CT, MRI, and ultrasound guidance are useful imaging tools for identifying these parasites and their complications.