Fibrosing mediastinitis / Mediastinal fibrosis:
Ill-defined mediastinal and bilateral hilar (right more than left) soft tissue is seen, showing hyperdense foci and calcification on the plain study and heterogeneous post-contrast enhancement.
The soft tissue encases and narrows the right pulmonary artery, the superior and inferior right pulmonary veins, the left superior pulmonary vein and the SVC. Resultant pulmonary venous hypertension is seen manifested as smooth septal thickening is seen in the right upper and lower lobes as well as in the left upper lobe. The right upper lobe bronchus is also encased and narrowed by the right hilar soft tissue.
Fibrosing mediastinitis is a rare benign disorder caused by proliferation of acellular collagen and fibrous tissue within the mediastinum. It can be idiopathic or secondary to infection like tuberculosis, histoplasmosis, sarcoidosis, radiation therapy and treatment with drugs like methysegide. It can have focal or diffuse forms. It commonly affects young patients with symptoms related to vascular and bronchial encasement and narrowing/ obstruction.
The imaging findings are often similar to malignancy and lung changes may resemble lymphanigitis spread. Hence it is important to differentiate this entity from malignancy and the best diagnostic clue is hyperdensity on plain study. The treatment options include steroids, surgical management and ballon dilatation or stenting of narrowed blood vessels or bronchi.
1. Imaging of granulomatous fibrosing mediastinitis. McNeeley MF, Chung JH, Bhalla S, Godwin JD. AJR Am J Roentgenol. 2012 Aug;199(2):319-27.
2. Fibrosing mediastinitis. Rossi SE, McAdams HP, Rosado-de-Christenson ML, Franks TJ, Galvin JR. Radiographics. 2001 May-Jun;21(3):737-57.
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