Hydatid disease

Dr Craig Hacking and A.Prof Frank Gaillard et al.

Hydatid cysts result from infection by the Echinococcus species, and can result in cyst formation anywhere in the body.

Cystic echinococcosus has a world wide geographical distribution. The Mediterranean basin is an important endemic area 6,7.

There are two main species of the Echinococcus tapeworm 1,2:

  • Echinococcus granulosus
    • more common
    • pastoral: the dog is the main host; most common form
    • sylvatic: the wolf is the main host
  • Echinococcus alveolaris/multilocularis
    • less common but more invasive
    • fox is the main host

Definitive hosts are carnivores (e.g. dogs, foxes, cats), and the intermediate hosts are most commonly sheep. Humans are accidental hosts, and the infection occurs by ingesting food contaminated with Echinococcus eggs 3.

The cysts usually have three components 1,2:

  • pericyst: composed of inflammatory tissue of host origin
  • exocyst
  • endocyst: scolices (the larval stage of the parasite) and the laminated membrane are produced here

Based on morphology the cyst can be classified into four different types 2:

  • type I: simple cyst with no internal architecture
  • type II: cyst with daughter cyst(s) and matrix
    • type IIa: round daughter cysts at periphery
    • type IIb: larger, irregularly shaped daughter cysts occupying almost the entire volume of the mother cyst
    • type IIc: oval masses with scattered calcifications and occasional daughter cysts
  • type III: calcified cyst (dead cyst)
  • type IV: complicated cyst, e.g. ruptured cyst

For hepatic hydatid infection on ultrasound also refer to World Health Organization 2001 classification of hepatic hydatid cysts.

A chest film or other plain films can be the first diagnostic modality when echinococcosis is suspected, depending on clinical indications. 

CT and MRI imaging are indicated when considering surgical treatment, particularly in regions like the brain, spine and locations inaccessible for conventional radiography or ultrasound, or in case of diagnostic uncertainty.

The Gharbi ultrasound classification consists of five stages 4:

  • stage 1: homogeneously hypoechogenic cystic thin-walled lesion 
  • stage 2: septated cystic lesion 
  • stage 3: cystic lesion with daughter lesions
  • stage 4: pseudo-tumor lesion 
  • stage 5: calcified or partially calcified lesion (inactive cyst)

Four treatment options are currently available 7:

  • surgical excision
  • PAIR (Puncture, Aspiration, Injection of protoscolicidal agent and Reaspiration)
  • chemotherapy with anti-helminthic agent (albendazole, mebendazole)
  • watch and wait for inactive and silent cysts

Treatment outcomes were improved when surgery or PAIR was combined with benzimidazole given before and after surgery 7. Regarding medical management, higher scolicidal and anti-cystic activity was seen in combination therapy with albendazole plus praziquantel and was more likely to result in cure or improvement 7.

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Article information

rID: 4875
Synonyms or Alternate Spellings:
  • Hydatid infection
  • Hydatid cyst
  • Hydatid infection - general
  • Echinococcosis

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Cases and figures

  • Figure 1: echinococcus life cycle
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  • Figure 2: microscopy-echinococcus granulosus scolex
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  • Figure 3: pathology photograph
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  • Figure 4: photograph - hydatid cyst membrane
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  • Figure 5: stages in liver
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  • Case 3: retroperitoneal hydatid
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  • Figure 6: pleural hydatid cysts
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  • Case 4: hepatic hydatid
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  • A well defined th...
    Case 5: pulmonary and hepatic hydatid
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  • Case 6: intracranial hydatid cyst
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  • Case 7: splenic hydatid cyst
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  • Case 8: intracranial hydatid cysts
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  • Case 9: pulmonary hydatid cyst
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  • Case 10: renal
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  • Case 11: hepatic, splenic and pulmonary hydatid cysts
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  • Case 12
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  • Case 13
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  • Case 14
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  • Case 15
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  • Case 16: in the neck
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  • Case 17: ruptured splenic hydatid cyst
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  • Case 18: multiple hepatic and pulmonary hydatid cysts
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  • Case 19: lung, liver and pericardial hydatid
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  • Case 20: intramuscular
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  • Case 21: pelvic hydatid cyst
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  • Case 22: hepatic, intra and retro peritoneal
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  • Case 23: peritoneal spread
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  • Case 24: disseminated hydatid disease
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  • Case 25
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