Ascariasis Workup

Updated: Oct 01, 2021
  • Author: Amber Mahmood Bokhari, MBBS; Chief Editor: Pranatharthi Haran Chandrasekar, MBBS, MD  more...
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Workup

Laboratory Studies

Stool examination for ova and parasites:

Visualization of large, brown 60 µm X 50 µm trilayered eggs is confirmatory. However, stool examination may be negative for ova for up to 40 days after infection because of the time needed for migration and maturation of the worm. The outer surfaces of fertilized eggs have an uneven mucopolysaccharide coat. Other parasitic coinfections can also be detected and are common. However, it may take 40 days for eggs to appear in the stools and if only infested with male worms, there may be no eggs at all.

Adult A lumbricoides worms can be visualized in the stool or the patient may notice them when passed. Mature worms are 35 cm long (females 20 to 35 cm; males 15 to 30 cm) and 6 mm in diameter. The worms are white or pink and are tapered at both ends.

Sputum examination:

Ascaris larvae may be observed in microscopic wet preparations of sputum during the pulmonary migration phase.

CBC with differential:

Results will reveal peripheral eosinophilia during the tissue migration phase of the infection. It may take weeks to resolve, but can be masked with the administration of steroids. It is more likely in the early lung phase than the late phase. [31, 37]

Serological tests:

Serum IgG and IgE are elevated during early infection, but this finding is not clinically useful.

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Imaging Studies

Radiologists practicing in Europe and North America should be familiar with unexpected but specific abnormalities associated with parasitic disease, especially in this age of increasing migration and tourism. [44]

Chest radiographs/CT chest: Images may show fleeting opacities during pulmonary migration. Bilateral, round infiltrates or ground glass opacities with ill-defined margins with variable sizes ranging from several millimeters to centimeters may be seen in patients with high eosinophilia. Infiltrates may show migratory pattern or become confluent as the worms move in the lung tissue.

Abdominal radiographs/ CT abdomen/ MRI:  Plain radiographs may show aggregated worms in the intestine, especially in children. A whirlpool pattern of intraluminal worms may be visible. Narrow-based air fluid levels without distended loops of bowel on upright plain films suggest partial obstruction. Wide-based air fluid levels with distended loops suggest complete obstruction. Barium swallow study may also reveal adult worms as filling defects or if ingested by worms show their alimentary canal. [16]  Worms have been increasingly identified in the biliary duct or gallbladder with ultrasonography and CT scanning. [45] Liver granulomata due to A suum infection have been described as ill-defined, 3- to 35-mm, nodular- or wedge-shaped lesions in the periportal or subcapsular regions.

Computed tomography (CT) scanning or magnetic resonance imaging (MRI) may demonstrate worms in the bowel. CT or MRI may demonstrate adult Ascaris worms in the liver or bile ducts in case of hepatobiliary disease. Magnetic resonance cholangiopancreatography (MRCP) may detect adult worms in bile or pancreatic ducts. Ultrasonography can also be useful for demonstration of hepatobiliary or pancreatic infestations.

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Other Tests

Endoscopic retrograde cholangiopancreatography (ERCP)  has become a commonly used procedure for both diagnosis of ascariasis and removal of worms from the biliary tract. The ease of diagnosis and therapy in the same setting makes ERCP particularly valuable when used with real-time ultrasonography. The combined procedures yield a sensitivity of nearly 100%. [41]

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