There is a particular kind of dread that comes with being handed a chest X-ray at three in the morning, on your own, with a sick patient and no radiologist for hours. The temptation is to glance at the obvious, decide it looks "probably fine", and move on. That glance is exactly how findings get missed. The antidote is not more knowledge — it is a system you run the same way every single time, so tiredness cannot steer you away from the thing that matters.
Start before you look at the lungs
The commonest error junior doctors make is diving straight for the interesting shadow. Discipline yourself to check the basics first, because they change how you read everything that follows.
- Details. Right patient, right date, and — easy to forget at night — is this the film you think it is, or an old comparison?
- Projection. Is it PA or AP? Portable films are almost always AP, which magnifies the heart and makes cardiomegaly hard to judge. Note it before you comment on heart size.
- Rotation, inspiration, penetration (RIP). Are the medial ends of the clavicles equidistant from the spinous processes? Can you count roughly five to seven anterior ribs above the diaphragm? Can you just see the vertebrae behind the heart? A rotated, under-inflated or over-penetrated film will lie to you, and you need to know that before you trust it.
A, B, C, D, E — but for the chest
Once you trust the film, walk through it in the same order every time. The letters are a scaffold; the point is that you never skip a region because your eye was drawn elsewhere.
A — Airway
Is the trachea central, or pulled or pushed? A deviated trachea is a loud clue: pushed away from a tension pneumothorax or large effusion, pulled towards collapse. Check the carina and the main bronchi while you are here.
B — Breathing (the lungs and pleura)
Divide each lung into upper, middle and lower zones and compare left with right, zone by zone. Symmetry is your friend — the eye spots a difference far more reliably than it judges an absolute. Look for areas of increased whiteness (consolidation, collapse, effusion, mass) and increased blackness (a pneumothorax, where you are hunting for a lung edge with no lung markings beyond it). Trace the pleural edges and both costophrenic angles; a blunted angle is often the first sign of a small effusion.
C — Circulation (the heart and mediastinum)
On a good PA film the heart should occupy less than half the chest width. Check the borders are crisp — a lost heart border points to adjacent consolidation (the silhouette sign). Glance at the mediastinal width and the aortic knuckle.
D — Diaphragm
The right hemidiaphragm normally sits a little higher than the left. Look under both domes for free air — a thin black crescent beneath the diaphragm means perforation until proven otherwise, and that is a phone call, not a wait-and-see.
E — Everything else
This is where tired eyes miss things, so make it deliberate. Check the bones for fractures and lesions, the soft tissues for surgical emphysema, and the review areas the eye habitually skips: the lung apices, behind the heart, the hila, and below the diaphragm. Then count the lines and tubes — is the NG tube below the diaphragm and bisecting the carina, is the central line tip at the cavoatrial junction, is there a pneumothorax after that line went in?
The findings that get missed are almost never invisible. They are in the review areas — the apices, behind the heart, the costophrenic angles — that the eye skips when it is tired and in a hurry.
The review areas, spelled out
Because they matter so much at night, it is worth naming them again as a deliberate second pass:
- Apices — small pneumothoraces and apical tumours hide here.
- Behind the heart — a left lower lobe collapse can lurk as a subtle triangle, and a hiatus hernia can masquerade as a mass.
- Hila — compare density and position; a bulky or displaced hilum is a real finding.
- Costophrenic angles — blunting is the earliest effusion sign.
- Below the diaphragm — free air and misplaced tubes.
Turning the film into a decision
Reading the image is only half the job; the other half is what you do next. Always interpret the film against the patient in the bed. A patchy shadow in a febrile, breathless patient is pneumonia to be treated tonight; the same shadow in someone well might be old scarring worth a comparison film. When you are genuinely unsure, that is not a failure — it is the moment to get help. Describe what you see plainly to a senior or the on-call radiologist rather than forcing a diagnosis you are not confident in.
The whole value of a system is that it is boring. It does not depend on you being clever or fresh; it depends only on you running it. Do it the same way on every film — the straightforward ones in daylight as much as the frightening ones at 3am — and the habit becomes automatic long before you actually need it under pressure. That is the point at which the dread starts to fade, because you know that whatever the film shows, you will not walk past it.