A mediastinal disease process may primarily involve a particular anatomic structure, or it may extend to another compartment. Because the mediastinum is frequently incomplete in dogs and cats, a disease process that begins in one hemithorax may extend to the other. The history that is most suggestive of a mediastinal disorder is recent trauma or invasive diagnostic or surgical procedures involving the head, neck, or thorax Survey radiography can show the location and extent of some mediastinal lesions; it can also suggest or rule out diagnostic differentials. Other diagnostic techniques, such as contrast radiography or thyroid scintigraphy, may be indicated. Ultrasonography can be used to guide thoracocentesis or percutaneous aspiration of a mediastinal mass. Exploratory thoracotomy may be needed for diagnostic evaluation as well as therapeutic intervention. Computed tomography and magnetic resonance imaging can provide useful information. This article discusses the diagnosis and treatment of various mediastinal disorders, including pneumomediastinum, mediastinitis, mediastinal mass, lymphadenopathy, and shifts in mediastinal position.
