Ascariasis is the commonest helminthic infection world wide and estimated to affect nearly 1 billion people (25% of population). The disease is transmitted by Ascaris lumbricoides which belongs to the nematode family (roundworms).
Infection occurs by ingestion of contaminated food (feco-oral route), the swallowed eggs hatch in the instestine giving rise to the larva which penetrates the intestinal mucosa and travel through the blood and lymphatics to the liver and lung. In the lung they maturate to form adult worm which then migrate though the airways to the larynx and pharynx and re-swallowed to the stomach as adult worms. They may remain in the intestinal lumen or penetrate the duodenal mucosa to the CBD.
The infected patients are usually asymptomatic however, migration through the lung may cause esinophilic pneumonia. Moreover, the adult worms cause mechanical obstruction to the intestinal lumen or may penetrate and obstruct the common bile duct leading to obstructive jaundice (Courvoisier sign if painless).
The adult worm can appear as longitudinal or curved filling defect within the intestinal lumen during contrast follow through study.
Identification of the long hyperechoic structure within the intestinal lumen with hypoechoic center (representing the worm alimentary tract) is highly suggestive.
Dilated CBD harbors a long curved hyperdense stucture with central hypodensity. Within the intestine they appear as filling defect within the contrast in the lumen.
Best non invasive method to detect biliary ascariasis. The worm appears as hypointense structure within the hyperintese CBD. With 3T MRI identification of the "three line sign" in thick slap MRCP confirm the diagnosis.
Gold standard but invasive method. It is used also in extraction of CBD worms.
Adult worms may cause CBD obstruction and recurrent cholangitis. Also they may aggregate within the intestinal lumen forming a mass and cause intestinal obstruction.
Endoscopic removal of CBD worms should be done under umbrella of antihelminthic therapy.
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