Imaging description

Fibrosing mediastinitis is a rare disorder which is caused by the buildup of collagenous and fibrous tissue within the mediastinum. It can present as either focal or diffuse mediastinal disease. The focal form will be seen as a hilar or mediastinal soft tissue mass and the diffuse form as mediastinal widening [1]. Infectious etiologies are associated with the focal form and present with calcified hilar and mediastinal nodes [1]. Granulomatous infections from Histoplasma capsulatum and Mycobacterium tuberculosis are the most common causes [2]. The diffuse form is usually associated with an idiopathic etiology and calcification is rarely seen. The accumulation of fibrotic tissue leads to compression of mediastinal structures such as the superior vena cava (SVC), pulmonary veins and arteries, central airways (trachea and main bronchi), and esophagus. Many of the clinical and radiographic manifestations are related to extrinsic compression of the central airways and vascular structures.

Airway obstruction causing lobar atelectasis or pneumonitis is common (Figure 28.1A). CT is excellent for demonstrating the presence of calcification (which can be extensive) within the hilar or mediastinal mass (Figure 28.1B) and the extent of soft tissue causing narrowing of mediastinal structures (Figure 28.1C). Parenchymal findings can occur from causes other than airway obstruction. Venous compression may cause pulmonary vein hypertension resulting in interstitial and alveolar edema (Figure 28.2A). Intravenous contrast is useful for assessing involvement of the SVC, pulmonary veins and arteries, and associated collateral vessels (Figure 28.2B).