A chest X-ray is one of the most common but technically challenging investigations in clinical practice.
To avoid “satisfaction of search”—the tendency to stop looking once you find one abnormality—you must use a repeatable, systematic approach.
Before applying the mnemonic, verify the 3 Ps:
Patient: Confirm Name, DOB, and Hospital Number.
Picture: Confirm the date and time the image was taken.
Position: Is it a PA (Posterior-Anterior) or AP (Anterior-Posterior) view?
Clinical Tip: PA is the standard. On an AP film, the heart appears larger due to magnification, making cardiomegaly difficult to diagnose.
Does the film RIP?
Rotation: The medial ends of the clavicles should be equidistant from the spinous processes of the vertebrae.
Inspiration: You should see 6 anterior ribs (or 10 posterior ribs) above the diaphragm. Poor inspiration can make the lungs look “congested” when they aren’t.
Penetration: You should just be able to see the vertebral bodies behind the cardiac silhouette.
Look for “Lions, Tigers, and Bears”—the hidden dangers.
Bones: Inspect the clavicles, ribs, and spine for fractures, lytic lesions (cancer), or osteoporosis.
Soft Tissues: Look for surgical emphysema (air under the skin) or breast shadows (is there a missing breast? think mastectomy).
External Hardware: Identify pacemakers, NG tubes, ET tubes, or central lines.
Heart Size: The Cardiothoracic Ratio (CTR) should be <50% on a PA film.
Hila: The left hilum is usually slightly higher than the right. Look for “bulky” hila, which may indicate lymphadenopathy or malignancy.
Mediastinum: Check for widening (Aortic Dissection) or tracheal deviation (Tension Pneumothorax or Goitre).
Shape: Hemidiaphragms should be dome-shaped. Flattening suggests hyperinflation (COPD/Emphysema).
Position: The right side is typically higher than the left (pushed up by the liver).
Below: Look for Pneumoperitoneum (free air under the diaphragm), which indicates a perforated bowel—a surgical emergency.
Costophrenic Angles: These should be sharp, “V-shaped” points.
Blunting: If the angles are rounded or “blunted,” this indicates a pleural effusion (fluid).
Divide the lungs into upper, middle, and lower zones and compare left to right.
Consolidation: Patchy white “shadowing” often indicates pneumonia.
Pneumothorax: Look for the absence of lung markings at the periphery and a visible “pleural line.”
Vessels: Lung markings should taper and become nearly invisible at the outer 1cm of the lung field.
Ensure the gastric bubble is on the left.
Situs Inversus: If the bubble is on the right and the heart points right (dextrocardia), the organs are mirrored.
Hiatus Hernia: A bubble behind the heart may indicate part of the stomach has moved into the chest.
Before finishing, re-scan these high-risk areas:
Apices: Easy to miss small tumors or TB.
Retrocardiac: Look “through” the heart for hidden consolidation.
Peripheral Margins: Check for small pneumothoraces.
Normal Film: “This is a PA chest X-ray of [Patient Name]. Technical quality is adequate. The trachea is central, the heart size is normal, and the lungs are clear with no effusions. This is a normal chest X-ray.”
Abnormal Film: “This is an AP film of [Patient Name]. There is dense opacification in the right lower zone with loss of the right hemidiaphragm, consistent with a right-sided pneumonia or effusion.”
1. What is the difference between a PA and AP view? In a PA view, the X-ray travels from back to front. This is the gold standard because the heart sits closer to the film, reducing magnification and giving an accurate heart size.
2. Why can’t I see the ribs clearly? This is often due to “Penetration.” If a film is under-penetrated, it looks too white; if over-penetrated, it looks too dark (burnt out), hiding lung detail.
3. What does “blunting of the costophrenic angle” mean? It means the sharp corner where the diaphragm meets the ribs is filled with fluid (pleural effusion) or scarring.
4. Can a chest X-ray rule out a Pulmonary Embolism (PE)? No. A chest X-ray is often completely normal in patients with a PE. A CTPA or V/Q scan is required for diagnosis.
Radiopaedia: Chest X-ray Summary – The global standard for radiology education.
Geeky Medics: CXR Interpretation – Excellent step-by-step clinical guide for students.
Radiology Assistant: Lung Disease – Advanced patterns of lung pathology.
NHS: Common X-ray Findings – Patient-facing info on what to expect.
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