Approach to Chest X-Rays
Atelectasis
Atelectasis is the loss of lung volume ranging from subsegmental collapse to entire lung collapse.
Atelectasis can be a Cause of: Direct Signs Indirect Signs (2o to volume loss) 1. Obstructive: most common and important type; collapse of alveoli develops within a few hours of airway obstruction as air dital to obstruction is reabsorbed. Can be secondary to neoplasm, foreign body, inflammation or mucous plug. 1. Lung fissure deviation 1. Hilar shift 2. Compressive: physical compression due to adjacent tumour, bulla, effusion, enlarged heart. 2. Increased opacity 2. Mediastinal shift 3. Passive: normal recoil of the lung in the presence of hydro- or pneumothorax. 3. Crowding of vessels 3. Diaphragm elevation 4. Cicatrization: fibrosis, most commonly secondary to prior granulomatous disease. 4. "Silhouette" sign 4. Compensating hyperinflation 5. Adhesive: thought to be due to loss of surfactant (e.g. hyaline membrane disease/RDS).
