Subpleural line refers to a thin curvilinear opacity, 1-3 mm in thickness, lying less than 1 cm from and parallel to the pleural surface. It corresponds to:
- atelectasis of normal lung if seen in the dependent posteroinferior portion of lung of a patient in the supine position (disappears if prone slices are obtained)
- pulmonary oedema
- fibrosis (other signs are usually present).
Though described in the context of asbestosis, this finding is not specific for asbestosis.