Fallen lung sign

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Definition
Fallen lung sign is finding of a collapsed lung or lobe in the setting of bronchial injury, and indicates a fractured bronchus. It occurs following complete rupture of bronchial main stem.

Following the bronchial injury, peripheral and posterolateral parts of the lung are collapsed.

Large pneumothorax develops and fails to resolve despite tube drainage. The lung falls inferiorly and laterally to the base of the hemithorax. If partial bronchial rupture occurs, the lung collapses medially and inferiorly.

Differential Diagnosis
None

Additional Resources

 * Medcyclopaedia - Traumatic rupture, tracheobronchial tree