• 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
• 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
• 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
• Nonparasitic cysts
• Hepatic neoplasm
• 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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