The chest radiograph is still the most requested imaging test in medicine. It is quick, cheap and low-dose — but it is also easy to misread. Most errors are not failures of knowledge; they are failures of search. A fixed routine, used every single time, is the best protection.
Before you look at the lungs
Confirm the patient, the date and the projection. A PA film taken standing is the reference standard; an AP film (often taken in bed) magnifies the heart and makes the mediastinum look wider than it is. Then assess image quality with four quick checks.
Quality checklist:
- Rotation – the medial ends of the clavicles should be equidistant from the spinous processes
- Inspiration – about 6 anterior ribs or 10 posterior ribs above the right hemidiaphragm
- Projection – PA or AP, erect or supine
- Exposure – vertebral bodies just visible through the heart shadow
The ABCDE sequence
Airway: the trachea should be central. Deviation can be pushed (tension pneumothorax, large effusion) or pulled (collapse, fibrosis). Follow the carina and both main bronchi.
Breathing: compare the lungs zone by zone, left against right. Look for consolidation, masses, nodules and loss of volume. Trace the pleural edge all the way round — a small apical pneumothorax is one of the classic misses.
Cardiac: on a good PA film the cardiothoracic ratio should be under 0.5. Check that the heart borders are sharp; loss of the right heart border suggests right middle lobe disease, and loss of the left border suggests lingular disease.
Diaphragm: the right hemidiaphragm usually sits slightly higher than the left. Look for free gas under the diaphragm and blunting of the costophrenic angles.
Everything else: bones, soft tissues, lines and tubes. Check the tip of every endotracheal tube, central line and nasogastric tube.
“The finding you are looking for is rarely the one you miss. The one you miss is the second abnormality on the same film.”
Review areas
When you think you have finished, look again at the places where pathology hides: the apices, behind the heart, below the diaphragm, the hila and the bones. Comparing with an earlier film, when one exists, is the single most useful thing you can do.
Bottom line
A systematic read takes about a minute once it becomes habit. Write down a structured report, state what is normal as well as what is abnormal, and always correlate with the clinical question.
This article is for education only and does not replace clinical judgement or local guidelines.
