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Essential Features

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  • • Hydatid disease caused by the microscopic cestode parasites Echinococcus granulosus and Echinococcus multilocularis

    • Form larval cysts in mammalian tissue

    • Foxes, coyotes, dogs, and cats are the definitive hosts that harbor the adult tapeworms in their intestines

    • Host animals are not harmed by the worms and are asymptomatic

    • Ova are passed in the feces and are ingested by intermediate hosts such as cattle, humans, rodents, and particularly sheep

    • Ova penetrate the intestine and pass via the portal vein to the liver (75%) and then to the lung (15%) or other tissues

    • Ovum typically develops into a cyst filled with clear fluid

    • Scoleces bud into the cyst lumen

    • Cysts grow slowly; patients may be asymptomatic for several years

    • Endocysts may cause secondary intraperitoneal cyst formation if spilled into the peritoneal cavity

    • 80% of hydatid cysts are single and in the right lobe

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Epidemiology

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  • • Most common cystic lesions of liver outside of the United States

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Clinical Findings

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Symptoms and Signs

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  • • Abdominal pain (especially in right upper quadrant)

    • Weight loss

    • Hepatomegaly

    • Jaundice

    • Portal hypertension

    • Hepatic mass

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Laboratory Findings

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  • • Eosinophilia is present in about 40% of patients

    • Serologic tests (eg, indirect hemagglutination, complement fixation, dot immunobinding, and ELISA) are specific and sensitive, yielding positive results in 80% or more of cases of hepatic hydatid cyst

    • Elevated liver function tests

    • Casoni skin test

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Imaging Findings

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  • US and CT scanning: Calcification and daughter cysts within the parent cyst

    Nuclear medicine imaging: Can also reveal uptake characteristic of hydatid cyst

    Abdominal x-ray: Can show calcific mass

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Diagnostic Considerations

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  • • Nonparasitic cyst

    • Cystic neoplasm

    • Hepatic malignancy (primary or metastatic)

    • Hepatitis

    • Hemangioma

    • Pyogenic abscess

    • Amebic abscess

    • Polycystic liver disease

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Rule Out

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  • • Nonparasitic cysts

    • Hepatic neoplasm

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Work-up

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  • • Complete history and physical exam

    • History of animal contact

    • Recent travel history

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Treatment and Management

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  • • In some patients, the parasite dies, the cyst wall calcifies, and therapy is not required

    • The surgical aim is to remove any cysts without disseminating the organism

    • Excision of the intact cyst

    • Scolicidal agent (hypertonic sodium chloride solution or sodium hypochlorite solution) can be placed into the cyst. Do not use alcohol because of fire risk.

    • Care must be taken to avoid rupturing the cyst and spilling its contents into the peritoneal cavity because of the dangers of anaphylaxis or implantation

    • Consider percutaneous drainage and albendazole

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Surgery

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Indications
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  • • Symptomatic and asymptomatic cysts, unless asymptomatic cysts ...

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