Heart failure and pulmonary oedema on chest X‑ray

Written by the X-Ray Atlas editorial team from the sources listed below · Medical review pending · Updated 24 October 2026 · Level: Beginner

Pulmonary oedema is excess fluid in the lung, first in the interstitium and then in the alveoli. The commonest cause is raised pulmonary venous pressure from left heart failure (cardiogenic oedema), but leaky capillaries (non-cardiogenic oedema, such as ARDS) and fluid overload produce similar pictures. The chest X-ray is quick, widely available and useful for supporting the diagnosis, gauging severity and looking for alternatives. It is not the test that diagnoses heart failure: in the UK that rests on clinical assessment, natriuretic peptides and echocardiography (NICE NG106).

1. The ABCDE signs

A common UK teaching mnemonic lists the main features:

	Sign	What you see
A	Alveolar oedema	Bilateral perihilar opacity, fading towards the periphery: the "bat's wing" or "butterfly" pattern
B	Kerley B lines	Short, thin horizontal lines at the lung periphery and bases, touching the pleura (interstitial oedema)
C	Cardiomegaly	Cardiothoracic ratio above 0.5 on a PA film
D	Dilated upper lobe vessels	Upper lobe diversion: upper-zone vessels as large as or larger than lower-zone vessels on an erect film
E	Effusions	Often bilateral; if one-sided, more often on the right

Additional signs include fluid in the fissures (thickened fissures, or a lens-shaped "pseudotumour" that vanishes with diuresis), peribronchial cuffing (thickened bronchial walls seen end-on as rings near the hila), perihilar haze with indistinct hilar vessels, and a widened vascular pedicle (the width of the upper mediastinum above the aortic arch; more than about 53 mm has been suggested to indicate volume overload [VARIES]).

Not every patient has every sign. A patient with acute heart failure after a myocardial infarction may have florid alveolar oedema with a normal-sized heart; a patient with chronic heart failure may have a large heart and effusions with clear lungs.

2. Heart size and the cardiothoracic ratio

A poor inspiration and prominent pericardial fat pads both overestimate the CTR. A large heart on X-ray may be dilated cardiomyopathy, valve disease or a pericardial effusion; a globular "water-bottle" shape and rapid change in size between films should raise the possibility of effusion, for which echocardiography is the test. The X-ray cannot reliably tell chamber enlargement from pericardial fluid.

3. How the signs progress

As pulmonary venous pressure rises, fluid moves first into the interstitium and then into the alveoli. Classic teaching links the signs to approximate pulmonary capillary wedge pressures (PCWP):

Approximate PCWP	Stage	Signs
About 13–18 mmHg	Redistribution	Upper lobe diversion
About 18–25 mmHg	Interstitial oedema	Kerley lines, peribronchial cuffing, perihilar haze, fissural thickening
Above about 25 mmHg	Alveolar oedema	Bat's wing perihilar consolidation, often with effusions

These figures are a teaching framework, not a measurement tool: the correlation is imperfect and varies between sources [VARIES]. There is also a time lag: radiographic changes can appear and clear up to about 12 hours after the pressure changes. A patient may improve clinically before the film does, and an early film may underestimate how unwell the patient is.

4. Kerley lines and other interstitial signs

• Kerley B lines: short (about 1–2 cm), thin, horizontal lines at the periphery of the lower zones, perpendicular to and touching the pleura. They represent thickened interlobular septa. Best seen at the costophrenic angles.
• Kerley A lines: longer (about 2–6 cm) oblique lines in the upper zones, running towards the hila.
• Kerley C lines: a fine reticular network; the term is now rarely used.

Septal lines are not specific to heart failure. Other causes include lymphangitis carcinomatosa (often with hilar nodes), interstitial lung disease, mitral stenosis, viral pneumonia and pneumoconiosis. See interstitial lung disease.

5. Cardiogenic versus non-cardiogenic oedema

Feature	Cardiogenic	Non-cardiogenic (for example ARDS)
Heart size	Often enlarged	Usually normal
Distribution	Central, perihilar, gravity-dependent	Patchy or peripheral
Septal lines	Common	Uncommon
Effusions	Common	Uncommon
Vascular pedicle	Often widened	Usually normal
Air bronchograms	Less common	Common

These are tendencies, and overlap is common. Fluid overload, for example in kidney failure, can look very like cardiogenic oedema. See the RadioGraphics review by Gluecker and colleagues for patterns.

Serial films and devices

On a ward or ICU, oedema is often followed with repeat films. When comparing, keep the technique in mind: a change from erect to supine, from PA to AP, or a poorer inspiration can make the heart look bigger and the lungs look wetter without any real change. Compare like with like where you can, and judge the overall trend rather than one film. Also look at the devices: pacemaker or defibrillator leads, valve replacements, sternotomy wires and central lines all tell you about the patient's cardiac history, and a new central line or pacing wire should prompt a check for pneumothorax. See pacemakers and cardiac devices.

6. Pitfalls and mimics

• Calling cardiomegaly on an AP film. Use clinical context and echo.
• Low-volume films crowd the basal vessels and widen the heart, mimicking oedema. Check inspiration.
• Bilateral pneumonia (including COVID-19), pulmonary haemorrhage, PCP and alveolar proteinosis can all look like alveolar oedema. Look at heart size, effusions, septal lines and how quickly the picture changes with treatment. See pneumonia.
• Unilateral oedema occurs, for example with the patient lying on one side or in severe mitral regurgitation, and can mimic pneumonia.
• Fissural fluid can look like a mass; it resolves with diuresis.
• Emphysema changes the pattern of oedema, making it patchy and atypical.
• A normal chest film does not exclude heart failure, particularly in chronic, compensated disease.

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	The ABCDE signs, how to measure the CTR and when not to, and the cardiogenic versus non-cardiogenic table.
Nurse	Recognise the patient who is getting more breathless and hypoxic, and understand why the film may lag behind the clinical change.
Junior doctor	Use the film to support the diagnosis and look for alternatives; arrange natriuretic peptide and echo; don't over-call AP heart size.
Radiographer	An erect PA film wherever the patient can manage it, labelled clearly, so heart size and diversion can be assessed.
Advanced / FRCR	Vascular pedicle width, chamber enlargement patterns, atypical oedema and the differential of septal lines.

Practise on heart failure films →

References

1. Radiology Masterclass. Heart failure. radiologymasterclass.co.uk
2. Radiopaedia. Kerley lines. radiopaedia.org
3. Radiopaedia. Cardiothoracic ratio. radiopaedia.org
4. Life in the Fast Lane (LITFL). Pulmonary oedema CXR. litfl.com
5. Gluecker T, et al. Clinical and radiologic features of pulmonary edema. RadioGraphics 1999;19:1507–1531.
6. NICE. Chronic heart failure in adults: diagnosis and management (NG106). nice.org.uk

For education only. Not a substitute for a formal report, senior review or your local policy. Never use this page to make decisions about a real patient.