Left Lower Lobe Atelectasis

Pathophysiology:  Atelectasis or volume loss can occur because of processes involving the wall or lumen of the bronchi, or pressure on the outside of the bronchus. Passive or relaxation atelectasis occurs when the intrapleural pressure becomes less negative (eg. with effusions or pneumothoraces).

Typical Left Lower Lobe Atelectasis:  Due to endobronchial tumor, usually a cancer or carcinoid tumor, or mucus plug or foreign body.

CXR Signs:  The typical “sail sign”: a triangular sail-like density seen behind the left heart shadow silhouetting out the left hemidiaphragm. On the lateral view the lower left major fissure deviates posteriorly.

Clinical Clue:  Atelectasis may predispose to post obstructive pneumonia which may be the clinical presentation.  In all patients, especially over the age of 45, follow-up is mandatory to exclude underlying cancer.

"Aunt Sophies": The problem is not the atelectasis, but any associated or precipitating tumor or pneumonia or foreign bodies (children) must always be considered and excluded.