Hydatid bone disease of the femur.

Osseous hydatid disease is caused by the parasitic tapeworm Echinococcus. The species most responsible for hydatid disease is Echinococcus granulosus, endemic especially in sheep-rearing districts like Mediterranean countries and Australia. In Turkey, the exact incidence of human hydatid disease is not known, but < or =34% of asymptomatic farmers have positive serology. Bone hydatidosis is rare, making up 0.5% to 4% of all cases. Patients usually present with pain, swelling, or pathological fracture. There are no specific radiographic signs in affected bone. In the later stages, lytic lesions with a trabeculated pattern, with or without sclerosis, may be seen. Computed tomography (CT) is still the best method for diagnosis and posttherapy follow-up of osseous hydatidosis. On CT, skeletal cystic hydatidosis appears as one or several closely related, well-defined, osteolytic lesions. There may be bone expansion, cortical thinning, cortical destruction, sclerosis, honeycomb appearance, and extension into adjacent soft tissues.