Internal Medicine


Echinococcosis is a parasitic disease of tapeworms of the Echinococcus type characterized by production of unilocular or multilocular cystic disease of lung and liver.

Echinococcosis is a parasitic disease of tapeworms of the Echinococcus type characterized by production of unilocular or multilocular cystic disease of lung and liver.


A. Cystic echinococcosis (M/C)

  • Also known as, unilocular echinococcosis
  • Caused by Echinococcus granulosus sensu lato

B. Alveolar echinococcosis (#2 M/C)

  • Also known as alveolar colloid of the liver, alveolar hydatid disease, alveolococcosis, multilocular echinococcosis, “small fox tapeworm”
  • Caused by Echinococcus multilocularis

C. Polycystic echinococcosis:

  • Also known as human polycystic hydatid disease, neotropical echinococcosis
  • Caused by Echinococcus vogeli and very rarely, Echinococcus oligarthrus.


Life cycle

The adult Echinococcus granulosus (3 to 6 mm long) [1] resides in the small bowel of the definitive hosts (dogs or other carnivores). Gravid proglottids release eggs [2] that are passed in the feces. After ingestion by a suitable intermediate host (under natural conditions: sheep, goat, swine, cattle, horses, camel), the egg hatches in the small bowel and releases an oncosphere [3] that penetrates the intestinal wall and migrates through the circulatory system into various organs, especially the liver and lungs. In these organs, the oncosphere develops into a cyst [4] that enlarges gradually, producing protoscolices and daughter cysts that fill the cyst interior. The definitive host becomes infected by ingesting the cyst-containing organs of the infected intermediate host. After ingestion, the protoscolices [5] evaginate, attach to the intestinal mucosa [6] and develop into adult stages [1] in 32 to 80 days. The same life cycle occurs with E. multilocularis (1.2 to 3.7 mm), with the following differences: the definitive hosts are foxes, and to a lesser extent dogs, cats, coyotes and wolves; the intermediate host are small rodents; and larval growth (in the liver) remains indefinitely in the proliferative stage, resulting in invasion of the surrounding tissues. With E. vogeli (up to 5.6 mm long), the definitive hosts are bush dogs and dogs; the intermediate hosts are rodents; and the larval stage (in the liver, lungs and other organs) develops both externally and internally, resulting in multiple vesicles. E. oligarthrus (up to 2.9 mm long) has a life cycle that involves wild felids as definitive hosts and rodents as intermediate hosts. Humans become infected by ingesting eggs , with resulting release of oncospheres in the intestine and the development of cysts in various organs. | By David Richfield (User:Slashme)When using this image in external works, it may be cited as follows:Richfield, David (2014). “Medical gallery of David Richfield”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.009. ISSN 2002-4436. – Image adapted from original available at the United States Centres for Disease Control Parasitology Identification Laboratory, Public Domain,


Hydatid cyst:

hydatid cyst is composed by two parts: the echinococcal parasite (or hydatid) and the adventitia that involves it, as Devé defined in the beginning of the last century (1911), and there is no reason or legitimacy to modify this definition. The adventitia is a layer of an inert tissue with fibrosis and variable thickness, which results from the host’s organ reaction against the hydatid, which is a foreign body. This layer can be called periparasitic or perihydatidic area, but never pericystic area, as it is sometimes wrongly named, because it is an integrant part of the cyst. An example of this common mistake is the use of the term “pericystectomy” for the excision of a cyst, when removing the adventitia. This term misleads you into thinking that this layer (adventitia) is not part of the cyst, assuming that the cyst includes only the parasite (hydatid) and not the adventitia, which is wrong and opposite to Devé’s definition
Hydatid cyst of the liver (scheme). | da Silva, A. M. (2010). Human Echinococcosis: A Neglected Disease. Gastroenterology Research and Practice, 2010, 583297.

Ultrasound (US) classification:

In 1981, Professor Gharbi et al. proposed a US classification of the hydatid cysts according the natural evolution of the parasite. In 1995, the Informal Working Group on Echinococcosis (IWGE-WHO) proposed the standardization of the US classification now known as WHO classification.
WHO US classification of hydatid cysts. | da Silva, A. M. (2010). Human Echinococcosis: A Neglected Disease. Gastroenterology Research and Practice, 2010, 583297.

Clinical feature

Symptoms occur due to mass effect of the cysts and are related to the organ in which they occur.

  • Liver cysts:
    • Abdominal pain & palpable mass
  • Lung cysts:
    • Chest pain, hemoptysis and breathlessness
  • Hydatid disease of the kidneys:
    • Hydatiduria
      • Passage of cysts in the urine
    • Hematuria following hydatiduria


Rupture or leakage from a hydatid cyst
  • Fever
  • Itching
  • Rash
  • Anaphylaxis
  • Dissemination of infectious scolices


  • Ultrasonography (USG) and CT scan
    • Internal membranes of cyst
    • Floating ectogenic cyst material (hydatid sand)
    • Daughter cysts within the parent cyst
  • Diagnostic aspiration
    • Generally contraindicated because of risk of infection and anaphylaxis
    • Antibody detection



Medical management

  • Albendazole or Mebendazole

PAIR (puncture-aspiration-injection-reaspiration):

First line management of hydatid cysts. Contraindicated in dead, calcified, deep-seated or multiloculated cysts
  • Puncture of cyst under image guidance
  • Aspiration of cyst contents
  • Instillation of hypertonic saline into cyst cavity
  • Reaspiration of the solution

Surgical management

  • Liver resection
  • Local excision of cysts
  • Deroofing + evacuation of contents


  • Proper cooking practices
Boiling sheep livers containing hydatid cysts for 30 minutes kills the cestode larvae – a simple method for prevention in remote areas | By Jun Li, Chuanchuan Wu, Hui Wang, Huanyuan Liu, Dominique Angèle Vuitton, Hao Wen and Wenbao Zhang – (2014). “Boiling sheep liver or lung for 30 minutes is necessary and sufficient to kill Echinococcus granulosus protoscoleces in hydatid cysts”. Parasite 21: 64. DOI:10.1051/parasite/2014064. ISSN 1776-1042., CC BY 2.0,

Leave a Reply

%d bloggers like this: