CT diagnosis of primary mediastinal hydatid cyst rupture into the aorta: a case report.

Primary hydatid cyst of the mediastinum is rare. We report a patient with a primary mediastinal hydatid cyst which ruptured into the aorta, resulting in bilateral popliteal embolism. The contrast-enhanced computed tomographic features represent a pathognomonic sign of a communicating rupture of an echinococcal cyst into the aorta. Comparison is made with ultrasonography and aortography.