Echinococcosis (hydatid disease)
Echinococcosis is a zoonotic tapeworm infection in which ingested Echinococcus eggs from dog feces grow into slowly enlarging hydatid cysts, most often in the liver and lungs. The diagnosis rests on characteristic imaging (anechoic cyst with daughter cysts, eggshell calcification) plus positive ELISA serology; small cysts are treated with albendazole and larger or complex cysts with albendazole plus percutaneous therapy or surgery, always guarding against cyst rupture and anaphylaxis.
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What this article covers
- Overview
A larval tapeworm infection that forms hydatid cysts: cystic echinococcosis (hydatid disease, hydatidosis) is caused by Echinococcus granulosus, the dog tapeworm, whose larvae grow into fluid-filled hydatid cysts in human organs.
- Epidemiology
Concentrated in rural areas of resource-limited regions: in those settings liver abscesses are usually caused by parasitic infections such as Echinococcus and Entamoeba histolytica.
- Risk factors
Close contact with dogs, the definitive host, whose feces carry the eggs.
- Pathophysiology
Egg ingestion: humans swallow Echinococcus eggs in food, water, or soil contaminated with dog feces.
- Clinical features
Asymptomatic incidental cyst, the most common presentation: incubation can last several years, and many cysts are found on imaging done for another reason.
- Differential diagnosis
Pyogenic liver abscess: an ill-appearing older patient with fever, leukocytosis with left shift, and raised bilirubin; aspiration yields pus with bacteria on Gram stain or culture, while a hydatid…
- Diagnosis
The diagnosis is established by characteristic imaging combined with positive Echinococcus serology: a smooth, round, anechoic cyst with daughter cysts, internal septation, or hydatid sand on…
- Management
First, if the cyst has ruptured and the patient has anaphylaxis, give epinephrine immediately: 0.3 to 0.5 mg IM into the anterolateral thigh (0.01 mg/kg, maximum 0.5 mg per injection), repeated every…
- Complications
Cyst rupture with anaphylactic shock: the most dangerous complication, from trauma, puncture, or surgery.
- Prognosis
Small cysts respond to medical therapy: cysts under 5 cm are treated with albendazole alone.
- Prevention
Avoid ingesting food, water, or soil contaminated with dog feces in endemic areas (rural sheep-raising regions, Alaska, the Upper Peninsula of Michigan, the southwestern United States).
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