Learning Radiology xray montage

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


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


  • “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


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

hydatid cyst of liver


hydatid cyst of liver


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