[Isolated retroperitoneal hydatid cyst. CT study. Apropos of a case].

A 30 year old patient with isolated retroperitoneal hydatid cyst was the first case of this type to be studied by CT scanning. Isolated retroperitoneal hydatid cyst is defined as any zone of hydatidosis occurring in the fatty tissue of the spaces lying behind posterior parietal peritoneum, without any parasitic foci in other organs. Differential diagnosis from other primary retroperitoneal cysts has been improved by the availability of modern imaging procedures: ultrasonography and CT scan.