Imaging diagnosis of musculoskeletal hydatid disease.

Hydatid disease has a worldwide distribution and causes health problems in endemic countries. Musculoskeletal hydatid disease may be a difficult differential diagnosis. The aim of this retrospective study is to present some different imaging features of musculoskeletal hydatid disease. We evaluated imaging findings of 15 patients with musculoskeletal hydatid disease over a 15-year period. Ten (67%) were men and 5 (33%) women, ages ranging between 12 and 69 years. All underwent radiographic evaluation. CT was done in 9 patients and MRI in 3 patients with soft tissue involvement. All underwent surgery, followed by histological examination. Bone involvement occurred in 11 patients and soft-tissue involvement in 4 patients respectively. Bone lesions in the spine were found in 4 (36%), in the pelvis 2 (18%), in the proximal femur 2 (18%), in the tibia 2 (18%) and 1 (9%) in the first metatarsal. On plain film we identified three different patterns of presentation of bone HD, defined as "typical" osteolytic lesion (33%), "tumour-like" features (41.6%) and lesions resembling infection (25%). Soft-tissue hydatidosis was localized on the distal part of the thigh, paravertebral and deltoid muscle. MR imaging showed a cystic mass, containing multiple vesicles, and in one of them the pathognomonic for hydatid disease, the "water lily" sign, was present. We present three cases of primary musculoskeletal hydatid disease localized on metatarsal bone, proximal femur and deltoid muscle. Musculoskeletal hydatid disease, presenting with a variety of patterns, may resemble a tumour or an inflammatory process. Because of the rare presentation of the disease it should be kept in mind in the diagnostic work-up of musculoskeletal tumours.