What are the pathophysiology and etiology of hydatid cysts?

Updated: Jun 12, 2018
  • Author: Robert E Glasgow, MD; Chief Editor: John Geibel, MD, DSc, MSc, AGAF  more...
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Answer

Hydatid cysts are caused by infestation with the parasite Echinococcus granulosus. This parasite is found worldwide, but it is particularly common in areas of sheep and cattle farming.

The adult tapeworm lives in the digestive tract of carnivores, such as dogs or wolves. Eggs are released into the stool and are inadvertently ingested by the intermediate hosts, such as sheep, cattle, or humans. The egg larvae invade the bowel wall and mesenteric vessels of the intermediate host, allowing circulation to the liver.

In the liver, the larvae grow and become encysted. The hydatid cyst develops an outer layer of inflammatory tissue and an inner germinal membrane that produces daughter cysts. When carnivores ingest the liver of the intermediate host, the scolices of the daughter cysts are released in the small intestines and grow into adult worms, thus completing the life cycle of the worm. [4, 5]


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