Spontaneous Chest Wall Interstitial Emphysema Secondary to Chronic Empyema Thoracis.

Spontaneous extension of air from the pleural space to the chest wall, also referred to as pneumothorax necessitans (PN), is a rare occurrence. Few of such cases have been reported in the literature, some appear to have a pattern of extension from pleural cavity to chest wall. Clinical conditions known to predispose to this complication are pneumothorax, empyema thoracis and tuberculosis of the pleural space or rib. We report a case of PN arising as complication of postpneumonectomy empyema (PPE) secondary to broncho-pleural fistula. Imaging features are highlighted emphasizing the likely pattern of spread.