Chest X-ray: a systematic approach

Key points

1. Check the patient details, date, projection (PA or AP), rotation, inspiration and penetration first.
2. A: airway and trachea; the trachea deviates away from a tension pneumothorax and towards collapse.
3. B: breathing; compare both lungs zone by zone, including behind the heart and below the diaphragm.
4. C: circulation; a cardiothoracic ratio above 0.5 on a PA film suggests cardiomegaly.
5. D and E: diaphragm (free air, blunted angles), then bones, soft tissues, lines and tubes.

Image guide

What to look for in each view of this topic.

1. Normal PA film. Clavicle heads equidistant from the spinous processes (no rotation), 5–6 anterior ribs visible above the diaphragm.
2. Right upper lobe collapse. Elevated horizontal fissure and tracheal shift to the right.
3. Left lower lobe collapse. Triangular density behind the heart with loss of the medial left hemidiaphragm (sail sign).
4. Tension pneumothorax. Hyperlucent hemithorax without lung markings, mediastinal shift away from the affected side.
5. Pleural effusion. Meniscus at the costophrenic angle; about 200 mL is needed to blunt the angle on a PA film.
6. Pneumoperitoneum. Crescent of free gas under the right hemidiaphragm on an erect film.