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Lung collapse: direct and indirect signs and lobar patterns
The direct sign of collapse is displacement of an interlobar fissure (with crowding of vessels and bronchi), and the indirect signs are pulling of structures toward the collapse — and lobar collapse in an adult requires a search for an endobronchial tumour.
Why it matters in the exam
The exam asks "what is a direct sign of collapse". The answer: fissure displacement, crowding of vessels and bronchi within the lobe, and increased density. Indirect signs: elevation of the diaphragm, shift of mediastinum and trachea toward the collapse, hilar displacement, rib crowding and compensatory hyperinflation of the other lobes. On CT a triangular lobe with a displaced fissure and concave margins is seen. Distinction from a large effusion: in collapse the whole white hemithorax pulls the mediastinum toward it; in a large effusion the mediastinum is pushed to the opposite side.
Patterns: right upper lobe — the minor fissure rises; with a hilar mass a reverse-S line appears (Golden S sign), suggesting an obstructing tumour. Left upper lobe — a grey "veil" over the upper half and the lobe moves forward; sometimes a band of air surrounds the aortic arch (Luftsichel). Middle lobe — loss of the right heart border. Lower lobes — a dense triangle behind the heart or beside the spine and loss of the diaphragm or descending aorta line; left lower lobe collapse appears as a "sail" behind the heart.
Mechanisms: obstructive (tumour, mucus plug, foreign body), passive or compressive (effusion, pneumothorax, as at the lung bases in heart failure), surfactant deficiency, and cicatricial (tuberculosis, radiation). Round atelectasis is a subpleural mass in a lower lobe beside pleural thickening — usually after asbestos exposure — with vessels and bronchi curving into it (a "comet tail") and lobar volume loss; it needs no biopsy when all the signs are present. In an adult with new lobar collapse — CT and bronchoscopy to exclude tumour. In a child — think first of a foreign body or mucus plug.
Key points
- Direct sign — fissure displacement.
- Indirect — diaphragm rises, mediastinum pulled.
- Golden S sign — collapse with a central tumour.
- Adult with collapse — CT and bronchoscopy.
- Round atelectasis — asbestos, comet tail.
Summary table
| Lobe | Sign on the PA film | Associated sign | Pitfall |
|---|---|---|---|
| Right upper | Minor fissure rises | Golden S sign with a hilar mass | Look for a central tumour |
| Left upper | Upper grey veil | Air band beside the aorta | There is no minor fissure on the left |
| Middle | Loss of the right heart border | Triangle on the lateral film | May look subtle |
| Left lower | Triangle behind the heart | Loss of the descending aorta and diaphragm lines | Look through the heart shadow |
| Whole lung | White hemithorax | Mediastinum pulled to the white side | Effusion pushes to the opposite side |
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Sources
- Fleischner Society: Glossary of Terms for Thoracic Imaging, 2024 — Atelectasis; Signs of lobar collapse
- British Thoracic Society Guideline for Diagnostic Flexible Bronchoscopy in Adults, 2013 — Indications
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.