Abstract
Cystic echinococcosis is a zoonotic disease caused by Echinococcus granulosus and causes significant morbidity, especially in endemic areas. It may remain asymptomatic for a long period. The clinical presentation depends on the exertion of pressure on adjacent organs or the sudden rupture of formed cysts. The presence of primary retroperitoneal echinococcal cysts, with no other organ involvement, has been scarcely reported in the literature. The aim of this study is to present the case of a 69-year-old male complaining of right flank pain for a month. Abdominal CT and MRI were performed, both revealing a large retroperitoneal mass measuring 18 centimeters in diameter, with daughter cysts and spots of calcification. The enzyme-linked immunosorbent assay (ELISA) for hydatid was positive. The patient denied any prior history of hydatidosis; thus, the diagnosis of a primary retroperitoneal echinococcal cyst was established. The patient underwent a successful total cystectomy and is in follow-up, reporting no recurrence of symptoms. Although the presence of echinococcal cysts in locations other than the liver or the lungs is rare, clinicians should always consider the possibility of a hydatid cyst diagnosis and perform the required diagnostic tests.