The Luftsichel Sign

A PA chest radiograph shows low left lung volume, haziness of the left lung with obliteration of the left heart border, a Luftsichel sign (arrowheads).
A lateral chest radiograph shows an anteriorly displaced left major fissure (arrows). The collapsed left upper lobe is up against the anterior chest wall.

Facts: Luftsichel sign

• Seen on PA chest radiograph of patients with left upper lobe collapse
• Paraaortic crescent of air with sharp margin extending anywhere from left apex to left superior pulmonary vein
• Luft = air; sichel = sickle [German]
• Caused by expansion of superior segment of left lower lobe due to left upper lobe collapse.
• In adults, it is an important clue to diagnose collapse that may be due to an obstructing endobronchial neoplasm.

Signs of Left Upper Lobe Collapse

• On PA view: Low left lung volume (elevated diaphragm), haziness of the left lung with obliteration of left heart border, elevated left hilum, near-horizontal course of the left main bronchus, Luftsichel sign
• On lateral view: Anteriorly displaced major fissure that parallels the anterior chest wall

Reference:

Blankenbaker DG. The Luftsichel sign. Radiology 1998;208:319-320.