The CT fallen-lung sign

On chest radiograph, the diagnosis of tracheobronchial tear is usually susp ected because of the persistance of a pneumothorax after chest tube inserti on. Since this radiographic pattern is nonspecific, thr diagnosis is usuall y made by bronchoscopy and delayed. The fallen-lung sign consists in the fa ll of the collapsed lung away from the mediastinum occuring when the normal central bronchial anchoring attachment of the lung is disrupted. In contra st to the persistent pneumothorax, this sign is specific but rarely observe d. Our purpose is to present the corresponding CT patterns observed in two cases of right stem bronchus tear. consisting in a caudal-dependent displac ement of the right upper lobe bronchus which becomes obliquely oriented.