Common and Rare Radiological Findings of Pulmonary and Thoracic Hydatid Cysts.

Clinical findings of pulmonary hydatid cysts (HCs) are generally nonspecific, with lower serological positivity than hepatic cases; therefore, radiological imaging serves as the primary diagnostic tool. Intact cysts on chest radiography present as well-defined, round or oval, homogeneous opacities. Computed tomography remains the gold standard for assessing intact and ruptured cysts, as it delineates internal architecture, membrane detachment, calcification, and relationships with adjacent structures. Magnetic resonance imaging offers complementary value, especially for mediastinal and chest wall cysts, owing to its superior soft-tissue contrast. Characteristic radiological signs after cyst rupture further aid diagnostic assessment. The "air crescent sign," "water lily sign," and "serpent sign" carry specificity close to pathognomonic value. Additionally, findings such as the "double dome arch sign" and "air bubble sign" aid in diagnosis. This review aims to provide a comprehensive examination of the radiological findings of pulmonary and thoracic HCs, highlighting the common and rare pathognomonic radiological signs reported in the literature. Cite this article as: Aydın Y, Durmaz F, Ulaş AB, Özgökçe M. Common and rare radiological findings of pulmonary and thoracic hydatid cysts. Eurasian J Med. 2026, 58(2), 1325, doi: 10.5152/eurasianjmed.2026.251325.