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Systematic chest radiograph reading, lines and tubes
Read a chest radiograph in a fixed order — quality (rotation, inspiration, projection), tubes and lines, airway, lungs and pleura, heart and mediastinum, diaphragm and bones — and use the silhouette sign to localise an opacity.
Why it matters in the exam
Quality first: good inspiration is 6 anterior ribs or 9–10 posterior ribs above the diaphragm; a supine AP film magnifies the heart and widens the mediastinum, so a cardiothoracic ratio above 0.5 means enlargement only on a PA film. The silhouette sign: loss of the border of a soft-tissue structure means an opacity lies against it — loss of the right heart border means the middle lobe, loss of the left heart border the lingula, and loss of the diaphragm line a lower lobe. An air bronchogram means alveolar filling (pneumonia, oedema, haemorrhage). The lateral view helps localise a finding seen on the PA view.
Pleural effusion: about 200 mL is needed to blunt the lateral angle on a PA film, while on a lateral film about 50 mL is enough in the posterior angle. A subpulmonic effusion appears as a "raised" diaphragm whose peak is shifted laterally, and on the left a large gap between the gastric bubble and the lung. Hyperinflated lungs: flat diaphragms, more than 10 posterior ribs and a large retrosternal space. Pneumothorax in a supine patient appears as the "deep sulcus sign". Suspected traumatic aortic injury: wide mediastinum, loss of the aortic knob contour, deviation of the trachea or nasogastric tube to the right, downward displacement of the left main bronchus and an apical pleural "cap" — and the diagnostic test is CTA.
Tubes and lines are a standard question: endotracheal tube tip in an adult 5±2 cm above the carina; central venous catheter tip in the lower superior vena cava or at its junction with the right atrium; nasogastric tube tip at least 10 cm beyond the gastro-oesophageal junction; tunnelled dialysis catheter — tip in the right atrium. In the newborn: umbilical venous catheter (UVC) tip where the inferior vena cava enters the right atrium, at T8–T9; high umbilical arterial catheter (UAC) between T6 and T10. After pneumonectomy the space gradually fills with fluid and the mediastinum shifts toward the operated side; a sudden fall in the fluid level or a shift to the opposite side raises suspicion of a bronchopleural fistula.
Key points
- Good inspiration — 6 anterior ribs.
- The silhouette sign localises the opacity.
- 200 mL to blunt the angle on PA.
- Endotracheal tube 5±2 cm above the carina.
- Wide mediastinum in trauma — CTA.
Summary table
| Finding | What it tells | Value or sign | Action |
|---|---|---|---|
| Loss of the right heart border | Middle lobe opacity | Silhouette sign | Lateral film or CT |
| Blunted lateral angle | Pleural effusion | About 200 mL on PA | US for volume and tapping |
| Wide mediastinum after trauma | Suspected aortic injury | Trachea and tube deviated to the right | CTA |
| Endotracheal tube tip | Tube position | 5±2 cm above the carina | Adjust if high or low |
| UVC tip in a newborn | Catheter position | IVC–right atrial junction, T8–T9 | Adjust if in the liver |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Diagnostic radiology, Medical licensing exam (IMLE), Internal medicine, Emergency medicine.
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Sources
- Fleischner Society: Glossary of Terms for Thoracic Imaging, 2024 — Radiographic signs
- ACR–SPR–STR Practice Parameter for the Performance of Chest Radiography, 2022 — Technique and image quality
- ACR Appropriateness Criteria: Intensive Care Unit Patients, 2020 — Routine and indicated chest radiographs; tubes and lines
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.