Pulmonary vasculitis is an inflammatory process involving the pulmonary vasculature that may cause destruction of the vascular wall with ensuing ischemic damage to lung tissue [ 1 ]. Vasculitis may occur in a variety of systemic and primary pulmonary vascular disorders. Most entities induce overlapping disease patterns such as pneumonitis with facultative capillaritis, diffuse alveolar damage, acute pulmonary hemorrhage, inflammatory obstruction of central pulmonary arteries down to small vessels with secondary pulmonary hypertension, or interstitial lung disease. Therefore, the clinical symptoms are nonspecific. An overlap of symptoms and the frequent lack of the full clinical picture limit the value of the established vasculitis classification systems of the Chapel Hill conference [2] (Table 1) and the American College of Rheumatology. It is in this light that a potential value of a morphologic categorization of vasculitic changes becomes apparent [3-13] (Table 2).
We have grouped pulmonary vasculitis along CT-morphologic patterns into entities characterized by large arterial aneurysmal versus stenotic disease, focal arterial versus diffuse alveolar hemorrhage, and pulmonary arterial hypertension. This article will familiarize radiologists with these features reflecting major processes of pulmonary vascular inflammation and describe ancillary CT findings that are helpful for the differential diagnosis.