Chest X-Ray Patterns and Signs
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Direct answer
Chest X-ray patterns and signs are read by locating an opacity against the heart, diaphragm and fissures, and the silhouette sign localises consolidation to a specific lobe. An air bronchogram indicates alveolar filling with patent airways, as in pneumonia or pulmonary oedema, while the Golden S sign points to a collapsed right upper lobe with a hilar mass. Lobar collapse shows volume loss with displacement of fissures and hilum.
What you must remember
- Silhouette sign: loss of the border of an adjacent structure when consolidation abuts it; right middle lobe disease obscures the right heart border, lingula disease obscures the left heart border, and lower lobe disease obscures the corresponding hemidiaphragm.
- Air bronchogram: visible air-filled bronchi within an opacity; it favours consolidation or oedema, because collapsed lung has no air in its airways.
- Golden S sign: a collapsed right upper lobe with a central hilar mass forming an S-shaped opacity, classically from a bronchogenic carcinoma.
- Right upper lobe collapse: upward shift of the horizontal fissure and elevated right hilum, with tracheal deviation towards the right.
- Left upper lobe collapse: a hazy, veil-like opacity over the upper and mid zone, with loss of the left heart and aortic knob outlines and an elevated left hilum.
- Kerley B lines: short horizontal septal lines at the lung periphery from interstitial oedema, typically seen in left ventricular failure.
- Hampton hump and Westermark sign: wedge-shaped pleural-based opacity and focal oligaemia suggesting pulmonary embolism.
Reading a film in four steps
A 62-year-old smoker presents with cough and a persistent chest film opacity, and the reader works through four questions in order. Each step narrows the differential before the next is asked.
- Density: The reader identifies whether the shadow is consolidation, collapse, mass or effusion.
- Location: The reader checks which heart border or hemidiaphragm is lost, for example the right heart border, which would place the disease in the right middle lobe.
- Volume: A shrunken lobe with a shifted fissure suggests collapse, whereas a normal-sized lobe with air bronchograms suggests consolidation.
- Hilar mass: A collapsed right upper lobe with a central mass forms the Golden S sign and mandates a CT.
A CT in this patient shows an obstructing central lesion, which turns the film from a pneumonia question into an oncology referral. The method is the same in any stem: density, location, volume, then the clue that changes the diagnosis.
Where the exam tries to catch you
Most traps here involve localising the lesion.
- Trap: confusing the right middle lobe with the lingula. Correct: both lose a heart border, but the right middle lobe obscures the right border and the lingula obscures the left.
- Trap: expecting an air bronchogram in collapse. Correct: collapsed airways contain no air, so the bronchogram is absent in collapse.
- Trap: mistaking the Golden S sign for a mediastinal mass. Correct: the S shape comes from the collapsed upper lobe, and the mass is central.
- Trap: attributing upper lobe volume loss to carcinoma at once. Correct: pulmonary tuberculosis commonly causes upper lobe volume loss with fibrosis that can mimic collapse, so tuberculosis is considered before carcinoma when the history is compatible.
Frequently asked questions
Which lobe's consolidation obscures the right heart border on a chest radiograph?
Right middle lobe consolidation or collapse obscures the right heart border, which is the silhouette sign for that lobe. The lingula, the left-sided equivalent, obscures the left heart border.
What does the Golden S sign indicate?
The Golden S sign describes a collapsed right upper lobe with a hilar mass, forming an S-shaped opacity on the chest film. It is classically associated with a central bronchogenic carcinoma that obstructs the right upper lobe bronchus.
Why does an air bronchogram favour consolidation over collapse?
An air bronchogram appears when air-filled bronchi stand out against alveoli filled with fluid or cells, as in consolidation. In lobar collapse the airways are themselves airless and the bronchogram disappears, so its presence supports pneumonia or pulmonary oedema.
What chest radiograph findings suggest left upper lobe collapse?
Left upper lobe collapse produces a hazy, veil-like opacity over the upper and mid zone, with loss of the left heart and aortic knob outlines and an elevated left hilum. The lobe collapses forwards and upwards, so there is no sharp upper zone shadow as in right upper lobe collapse.