hydatid /hī″dətid/ [Gk, hydatis, water drop] , a cyst or cystlike structure that usually is filled with fluid, especially the cyst formed around the developing scolex of the dog tapeworm. Humans and sheep can become hosts to the larval stage by ingesting the eggs. Hydatid cysts may be identified by palpation. They occur most commonly in the liver. An acute anaphylactoid allergic reaction may occur if the cyst ruptures. See also hydatid cyst, hydatid mole, hydatidosis. −hydatic, adj.
