hydatid

(hī'də-tĭd)

1. A cyst formed as a result of infestation by larvae of the tapeworm Echinococcus granulosus.
2. The encysted larva of E. granulosus.

[Greek hudatis, hudatid-, watery vesicle, from hudōr, hudat-, water.]

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1. A hydatid cyst.
2. The encysted larva of Echinococcus granulosus.
3. An abnormal vascular structure that is usually filled with fluid.

1. a hydatid cyst.
2. any cyst-like structure.

• h. cyst — the larval stage of the tapeworm Echinococcus granulosus or E. multilocularis, containing daughter cysts, each of which, if fertile, will have many protoscoleces; it is the cause of hydatid disease. Called also Echinococcus cyst and hydatid.
• h. disease — an infection in humans, sheep, cattle, pigs and horses, and occasionally in many other mammal species. The infection is usually of the liver or lungs, caused by larval forms (hydatid cysts) of tapeworms of the genus Echinococcus, and characterized by the development of expanding cysts. In the infection caused by E. granulosus, single or multiple cysts that are unilocular in character are formed, and in that caused by E. multilocularis, the host's tissues are invaded and destroyed as the cyst(s) enlarge by peripheral budding. Called also echinococcosis.
• false h. — see cysticercus tenuicollis.
• Morgagni's h. — see morgagni's hydatid.
• sessile h. — the hydatid of Morgagni connected with a testis.
• stalked h. — the hydatid of Morgagni connected with an oviduct.