Echinococcus cyst

Echinococcus cysts, also called hydatid cysts, occur as a consequence of consuming something contaminated by echinococcal tapeworm’s eggs. An example of contamination is drinking water which is infested by dog faeces, or not washing your hands after petting a dog or cat and then touching food. When the eggs are ingested, they hatch in the intestines and the adult tapeworms penetrate the intestinal wall. This gives them the ability to travel with the blood stream or the lymphatic circulation, and they often end up in the liver where they die and form a hydatid cyst. This cyst can grow and compress the structures in the liver and around, destroying the liver parenchyma in the worst case.

These cysts are often solitary, but they can be multiple. This occurs if the parasites can spread throughout the biliary tree before dying.

Clinical features

The incubation time is long (up to 50 years!), and the cyst shows usually no symptoms. However, the patients may experience pain in the upper right quadrant and hepatomegaly. Rupture of these cysts can cause anaphylaxis and death, so surgery is needed to remove them as soon as possible.

Diagnosis and evaluation

Calcified wall on CT, a positive ELISA, and eosinophilia are characteristic features of echinococcus cyst. These cysts may look solid on imaging and can therefore be mistaken for a tumor.

Treatment

Echinococcus cysts should be removed surgically. It’s important to remove the whole cyst without spilling its contents, as it could cause anaphylaxis. Antiparasitic treatment with mebendazole may be considered as the only treatment in small cysts, or as a complement to surgery.