CHAPTER ELEVEN MEDIASTINUM AND HILA

CHAPTER ELEVEN MEDIASTINUM AND HILA

This chapter will review the radiologic approach to mediastinal masses, diffuse mediastinal disease, and hilar abnormalities.

MEDIASTINAL MASSES

Localized mediastinal abnormalities are common diagnostic challenges for the radiologist. Patients with mediastinal masses tend to present in one of three ways: one with symptoms related to local mass effect or invasion of adjacent mediastinal structures; two as the result of a search for mediastinal abnormality in a patient with a predisposing condition; or three as an incidental finding on chest radiography or CT. Occasionally, a mediastinal mass is discovered in the course of an evaluation for known malignancy. Contrast-enhanced multidetector row CT is the primary cross-sectional modality used to evaluate mediastinal masses. MR is typically reserved for specific problem solving and is most useful for: one assessing lesions in patients who cannot receive iodinated contrast; two likely vascular lesions; three confirming the cystic nature of lesions that have high attenuation due to proteinacious contents; and four distinguishing thymic hyperplasia from thymic neoplasms. PET is used to confirm increased metabolic activity in suspected malignancy, to assess response of mediastinal tumors to therapy, particularly lymphoma, and to distinguish residual or recurrent tumor from fibrosis.

For the purposes of the following discussion, the mediastinum is divided into three compartments: anterior, middle, and posterior compartments, as described in Chapter Ten.