Hydatid disease of bones – Imaging spectrum

Hydatid cyst, caused by echinococcus granulosa, can produce tissue cyst everywhere in body. Skeletal cystic lesion is rare specially in long bones like femur and because of its unusual presentation, its diagnosis may easily be missed, unless be kept in mind. Hydatid disease is a parasitic infestation of the humans that can practically affect any part of the body. It commonly affects liver, lung and muscles. Bone hydatid is less common occurring in only 0.5–2% of cases and humans act as an intermediate host. In the patient evaluated by us, the plain x-ray showed multiple osteolytic lesions along the lower one third of the femur and the upper end of tibia. There was also cortical destruction of the joint surfaces that is seen with involvement of the joint. USG revealed a well-defined anechoic cystic lesion in the region of the calf in the substance of gastrocnemius muscle with fine septation and fine echogenic debris in the dependent part. MRI further provided data on the involvement of bone marrow and the extent of the disease. In the second patient, there was hydatid affection of the sacrum and spinal canal. The diagnosis was confirmed on tru-cut biopsy from the affected bone. Primary hydatid disease is a very rare entity and can be seen without evidence of any other visceral involvement. Cautious suspicion of the disease and early diagnosis is important for the management.