Gallengangsaskariden

Biliary
ascariasis causing cholelithiasis in a child. A non-mobile, echogenic focus without posterior acoustic shadowing is seen within the gallbladder with associated thickening of the gallbladder wall. No evidence of a calcified stone within the gallbladder or the visualized biliary tree.
www.eurorad.org • CC by-nc-sa-4.0
Biliary
ascariasis causing cholelithiasis in a child. Dilated common bile duct measuring 0.79 cm. No echogenic or shadowing focus identified. The other parts of the biliary tree were not fully visualized due to overlying intestinal gas.
www.eurorad.org • CC by-nc-sa-4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

Gallengangsaskariden

Ascariasis is the commonest helminthic infection worldwide and estimated to affect nearly 1 billion people (25% of the population). The disease is transmitted by Ascaris lumbricoides which belongs to the nematode family (roundworms).

Lifecycle

Infection occurs by ingestion of contaminated food (faeco-oral route), the swallowed eggs hatch in the intestine giving rise to the larvae which penetrate the intestinal mucosa and travel through the blood and lymphatics to the liver and lung. In the lung, they maturate to form adult worms which then migrate through the airways to the larynx and pharynx and are re-swallowed into the stomach as adult worms. They may remain in the intestinal lumen or penetrate the duodenal mucosa to pass into the CBD.

Pathogenesis

The infected patients are usually asymptomatic, however, migration through the lung may cause eosinophilic 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).

Radiological features

Fluoroscopy

The adult worm can appear as a longitudinal or curved filling defect within the intestinal lumen during a contrast follow through study.

Ultrasonography

Identification of the long hyperechoic structure within the liver with hypoechoic center is highly suggestive.

CT

Dilated CBD harbors a long curved hyperdense structure with central hypodensity. Within the intestine, they appear as a filling defect within the contrast in the lumen.

MRCP

Best non-invasive method to detect biliary ascariasis. The worm appears as a hypointense structure within the hyperintense CBD. With 3T MRI identification of the "three line sign" in thick slab MRCP confirms the diagnosis.

ERCP

Gold standard but an invasive method. It is used also in the extraction of CBD worms.

Prognosis

Adult worms may cause CBD obstruction and recurrent cholangitis. Also, they may aggregate within the intestinal lumen forming a mass and cause intestinal obstruction.

Treatment

Endoscopic removal of CBD worms should be done under the umbrella of antihelminthic therapy.

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Gallengangsaskariden:
Ascaris
lumbricoides
Wikipedia • Public domain