Bone versus soft tissue hydatid disease: a retrospective comparative cohort study

BACKGROUND: Musculoskeletal hydatid disease is uncommon and often mimics neoplastic lesions. Comparative evidence between bone and soft tissue involvement remains limited. We aimed to compare demographic characteristics, laboratory parameters and surgical outcomes between bone and soft tissue hydatid disease in an endemic region. METHODS: We retrospectively reviewed 64 consecutive patients who underwent surgery for histopathologically confirmed musculoskeletal hydatid disease between January 2010 and January 2024 (bone, n = 26; soft tissue, n = 38). Groups were compared regarding demographics, presenting symptoms, inflammatory indices White Blood Cell Count (WBC), Erythrocyte Sedimentation Rate (ESR), and C-Reactive Protein (CRP), Eosinophil count, Eosinophil-to-Lymphocyte Ratio (ELR), hemagglutination test, cyst morphology (uni- vs. multilocular), complications, concomitant liver/lung involvement, and recurrence. Appropriate parametric/non-parametric and categorical tests were used. RESULTS: Demographic characteristics and baseline WBC/ESR/CRP and hemagglutination positivity did not differ between groups. Bone involvement presented predominantly with pain (22/26, 84.6%), whereas soft tissue disease frequently presented with isolated swelling (20/38, 52.6%) (p = 0.001). Eosinophil count (2.00 ± 1.26 vs. 0.89 ± 0.68; p = 0.013) and ELR (0.23 ± 0.13 vs. 0.12 ± 0.08; p = 0.014) were significantly higher in bone disease. Bone involvement had higher rates of intraoperative rupture (20/26, 76.9% vs. 10/38, 26.3%; p = 0.005), concomitant organ involvement (14/26, 53.8% vs. 8/38, 21.1%; p = 0.045), and recurrence (20/26, 76.9% vs. 8/38, 21.1%; p = 0.002). Multiloculated morphology was more frequent in soft tissue lesions (30/38, 78.9% vs. 10/26, 38.5%; p = 0.005). Among the cases treated for bone hydatid cysts, recurrence was observed in 20 out of 26 patients, while anaphylaxis occurred in 15 out of 26 patients during surgery. In contrast, among 38 patients who underwent surgery for soft tissue hydatid cysts, recurrence was observed in 8 (p = 0.002) and anaphylaxis developed in 7 during surgery (p = 0.041). CONCLUSIONS: Bone hydatid disease demonstrates a more aggressive clinical course than soft tissue disease, with substantially higher rupture, recurrence, and concomitant organ involvement rates. Elevated eosinophil count and ELR at presentation may support the suspicion of bone involvement. Future prospective studies incorporating multivariable modeling are warranted to identify independent predictors of recurrence.