Hydatid Cyst of the Liver
Cystic Echinococcosis

General Considerations

• Parasitic infestation caused by Echinococcus tapeworm
• Endemic to Middle East, Africa, Iceland, Australia, southern parts of South America
  • Very rare in US
• Cysts grow slowly and usually don’t become symptomatic until adulthood (30-50 years old)
• Three species which cause human disease are
  • E. granulosus (aka granulosa, granulosis) causes Cystic Echinococcosis (CE) (most common)
  • E. multilocularis causes Alveolar Echinococcosis (AE) –most virulent
  • E. vogeli—rarest
• Infestation of humans, who are accidental intermediate hosts, occurs from ingestion of water or food contaminated by fecal material of definitive hosts (dogs, wolves, deer, sheep, coyotes)
  • Eggs hatch in duodenum and pass as larvae through intestinal wall into blood stream to liver and lungs

Clinical Findings

• Asymptomatic in many cases
  • Most symptomatic cysts are 5 cm or more
• Symptoms frequently come from pressure on affected organs
  • Jaundice, abdominal pain if in liver
• Cough, dyspnea and chest pain if in lungs
• Other symptoms arise from leakage of cyst contents or infection of cyst
• Pain, flushing and urticaria
• Anaphylactic reaction
• Fever and sepsis
• Liver is most common organ involved (mostly right lobe)
  • Then, lungs, muscles, bones kidneys, brain and spleen, in order

Imaging Findings

• Conventional radiographs
  • May show a rim-like calcification in liver cyst
• Cavity in lung
• CT is most accurate
• Low density, fluid-filled masses
• May have septations
• Wall may be calcified or enhance with contrast
• Wall is frequently of high density even without contrast-enhancement
• Internal calcifications may also occur
• There may be multiple daughter cysts
• Inner layer of cyst may separate from outer layer and appear as a serpentine structure inside of the cyst
  • Water-lily sign is characteristic of hydatid cyst
• Multilocular cysts may have a honeycomb pattern from septations
• US
  • Usually echogenic because of daughter cysts or infolded membranes
• Daughter cysts can be either echogenic or non-echogenic
• Fragments may be seen in common bile duct

Differential Diagnosis

• Hepatocellular carcinoma
• Liver abscess
• Hepatic cysts
• Amebic cysts
• Calcifying lesions in the liver

Treatment

• For Cystic Echinococcosis, surgery is most frequently used
• Repeated aspiration of cysts with injection of anti-helminthic agent
• Chemotherapy includes use of benzimidazoles

Complications

• “Metastases” can occur in lung, brain or bone
• Complications, including anaphylaxis, come from
  • Rupture of cyst (intra-biliary rupture is most common)
• Infection of cyst
• Biliary obstruction
• Cirrhosis Bronchial obstruction
• Urinary tract obstruction

Prognosis

• With Cystic Echinococcosis, prognosis is good with surgical excision without spillage
• In Alveolar Echinococcosis, 10-year mortality rates of 10%

Hydatid Cyst of the Liver. Black arrows point to a cystic lesion on the right lobe of the liver containing dense calcifications. The cyst was excised.
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Hydatid Cysts  eMedicine   Dandan, I; Soweid, A and Abiad, F
Imaging Appearances Of Hydatid Cyst Ds Shah, H Parikh, B Shah, S Banuprakash, J Shah Ind J Radiol Imag 2006 16:4:533-535
Hydatid cyst of the liver: rupture into the biliary tree. L Marti-Bonmati, F Menor, and A Ballesta. American Journal of Roentgenology, Vol 150, Issue 5, 1051-1053