Focal or diffuse lesions of the central airways are produced by a variety of diseases. The etiology includes infection, malignancy, trauma, aspiration, collagen vascular disease, and idiopathic entities such as sarcoidosis, amyloidosis, or tracheopathia osteochondroplastica. Even though patients may present with significant symptomatology, these airway abnormalities are frequently not apparent or are overlooked on chest radiographs. Thus, diagnosis is often delayed. If there is a clinical or radiographic suspicion of tracheobronchial abnormality, furthur evaluation on CT is warranted. In particular, helical CT permits excellent multiplanar reconstructions, which are especially useful for surgical planning.
This pictorial essay concentrates on CT techniques useful in central airway evaluation and on the diseases that cause focal airway abnormalities. We recognize that the distinction of focal and diffuse airway abnormalities is somewhat arbitrary and is complicated by the fact that many diseases can cause either focal or diffuse airway narrowing. For purposes of this review, however, we will discuss the diseases that most commonly affect the airway in a focal manner, and we will discuss the diseases that often result in long-segment or multifocal disease in a separate review.