Echinococcosis

• • 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

Epidemiology

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

Symptoms and Signs

• • Abdominal pain (especially in right upper quadrant)

  • Weight loss

  • Hepatomegaly

  • Jaundice

  • Portal hypertension

  • Hepatic mass

Laboratory Findings

• • 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

Imaging Findings

• • 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 cyst

  • Cystic neoplasm

  • Hepatic malignancy (primary or metastatic)

  • Hepatitis

  • Hemangioma

  • Pyogenic abscess

  • Amebic abscess

  • Polycystic liver disease

Rule Out

• • Nonparasitic cysts

  • Hepatic neoplasm

• • Complete history and physical exam

  • History of animal contact

  • Recent travel history

• • 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

Surgery

Indications

• • Symptomatic and asymptomatic cysts, unless asymptomatic cysts completely circumferentially calcified

  • Abdomen explored and cysts are isolated

  • Superificial cysts may be excised

  • Large cysts may be unroofed and ...