The excised hydatid cysts shown here are a beautiful example of a parasitic (tapeworm!) infection with Echinococcus sp. Although the liver is the most common organ involved, hydatid cysts can be found in the lungs, muscle, brain and kidneys. A cyst in the liver < 5 cm should not cause symptoms.
Liver involvement may be reflected in an elevated bilirubin or alkaline phosphatase level. Leukocytosis may suggest infection of the cyst. Eosinophilia is present in 25% of all persons who are infected, while hypogammaglobinemia is present in 30%. A positive Echinococcal antibody is not specific for the disease, and a confirmatory antibody test can be sent to the CDC (Center for Disease Control) to make a firmer diagnosis when there is still concern.
If treatment is indicated, albendazole, mebendazole or praziquantel has been used in the past. Treatment may last several months. Surgical excision, as in the case above, is another option. Aspiration is a less-palatable option; the risk of leakage and anaphylaxis is a major concern.