Biliary Ascariasis

Ascariasis is a common helminthic infestation found worldwide, being especially prevalent in the tropics. In the United States it occurs in the deep South. The adult Ascaris lumbricoides worm lives in the intestinal tract where it produces few symptoms. Biliary obstruction, cholangitis, cholecystitis, pancreatitis, and an intrahepatic abscess are complications if an adult worm migrates into the bile ducts. Biliary ascariasis is more common in children than in adults. Several reports have commented on a sphincterotomy predisposing to biliary infestation.
Computed tomography identifies a worm as a hyperdense tubular structures surrounded by bile. When viewed in a transverse section, the worm has a “bull’s-eye” appearance. Several worms, especially if coiled, appear as an intraluminal tumor. Ultrasonography reveals a worm as a tubular hyperechoic structure within the bile ducts or gallbladder. At times worm motion is identified. A long curved, tubular, nonshadowing structure containing a hypoechoic center, called the impacted worm sign, is occasionally
identified in intrahepatic ducts; macerated round worms are seen as focal intraluminal soft tissue masses, with the US appearance mimicking a cholangiocarcinoma. Magnetic resonance cholangiopancreatography has detected a hyperintense signal inside the worm digestive tract, presumably due to fluid in its gut. The diagnosis is also established by ERC, and this technique is then used to remove the worm.
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Radiology images of Biliary ascariasis.Ultrasonography shows a tubular hyperechoic structure (arrow) in the common bile duct.
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