Mediastinal bronchogenic cyst: demonstration of a fluid-fluid level at MR imaging.

The appearance of mediastinal bronchogenic cysts at cross-sectional imaging is variable. Intracystic hemorrhage, proteinaceous fluid, or suspended calcium may belie the true cystic nature of the lesion at computed tomography or magnetic resonance (MR) imaging. The authors report a case of a fluid-fluid level seen on MR images of a bronchogenic cyst. This appearance, likely due to dependent layering of proteinaceous material, helped preoperatively confirm the true cystic nature of the lesion.