[Splenic-thoracic transit: a rare evolution of hydatid disease].

We report a case of splenic hydatid cyst, an unfrequent localization of hydatid disease that usually presents with hydatid cysts in other organs (but not in this case). Primary spleen infestation generally occurs trough arterial blood supply, after the oncosphere of Echinococcus granulosus travels from host's digestive tube to the left atrium, passing trhough hepatic and pulmonar filters; other routes are also possible. Migration of an abdominal hydatid cyst into the thoracic cavity (phenomena called abdominal thoracic hydatid transit) occurs in 3.5% to 5% of liver cysts, and is quite exceptional in splenic cysts. Clinical manifestations are mainly thoracic, the diagnosis is based on serological tests and imaging studies, and surgical treatment is always required. Taking advantage of this unusual case, we remember the pathogenesis of splenic hydatid disease as well as the pathophysiology of transdiaphragmatic transit of abdominal hydatid disease.