[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Radiology](https://durgical.com/en/radiology/) › [Chest](https://durgical.com/en/radiology/areas/chest/) › Cardiomegaly and pulmonary oedema on the chest X-ray # Cardiomegaly and pulmonary oedema on the chest X-ray - Finding In heart failure the heart looks big and fluid backs up into the lungs. The X-ray shows the fluid in a set order, from vessels to septa to air spaces. Updated Nov 12, 2026 ## Key points - Cardiomegaly = cardiothoracic ratio above 0.5 on an upright PA film, not on AP. - Order: upper-lobe diversion, then Kerley B lines and cuffing, then bat-wing alveolar oedema. - Bilateral effusions, often right more than left. - Normal heart, no septal lines, peripheral opacity: think ARDS rather than cardiac oedema. ## What it is Rising pressure in the left atrium and pulmonary veins shows on the chest X-ray in stages. First the upper-lobe vessels become as wide as or wider than the lower-lobe ones (upper-lobe diversion). Then fluid leaks into the interstitium: short horizontal lines at the lung bases (Kerley B lines), thickened fissures, cuffing around bronchi seen end-on and blurred hila. Finally fluid floods the alveoli: bilateral hazy opacity spreading from the hila (the bat-wing pattern), often with air bronchograms and bilateral effusions. The heart is often enlarged: a cardiothoracic ratio above 0.5 on a PA film. The order helps tell cardiogenic oedema from lung injury (ARDS). ## What it looks like - Cardiothoracic ratio: widest heart diameter over widest inner chest diameter; above 0.5 on an upright PA film is cardiomegaly. - Stage 1, venous congestion: upper-lobe vessels equal to or wider than lower-lobe vessels. - Stage 2, interstitial oedema: Kerley B lines (short, horizontal, at the bases, touching the pleura), peribronchial cuffing, thick fissures. - Stage 3, alveolar oedema: bilateral perihilar bat-wing opacity, air bronchograms. - Pleural effusions, usually bilateral and often larger on the right; fluid in a fissure can look like a mass. - A globular, water-bottle heart with clear lungs suggests pericardial effusion rather than heart failure. ## Why it looks that way - Raised pulmonary venous pressure pushes fluid out of the capillaries into the interstitium, then into the alveoli. - Kerley B lines are thickened interlobular septa filled with fluid, seen edge-on at the lung periphery. - Upright, gravity normally makes lower-lobe vessels larger; congestion reverses that pattern. ## Differential and pitfalls - An AP or supine film magnifies the heart: do not call cardiomegaly on it, but a normal size on AP is truly normal. - Poor inspiration crowds the bases and makes the heart look bigger. - ARDS (non-cardiogenic oedema): normal heart size, no septal lines, more peripheral patchy opacity, few effusions. - Bilateral pneumonia can look like oedema; fever, clinical course and quick response to treatment help separate them. - Radiographic signs lag behind pressures: the film may look worse or better than the patient for hours to days. ## Next step - Echocardiography to measure ventricular function, valves and the pericardium. - Natriuretic peptide, ECG and troponin as the clinical picture requires. - Lung ultrasound at the bedside: several B-lines in both lungs support oedema and follow the response. - Do not repeat the X-ray daily to follow treatment; repeat for a clinical change or a new problem. - Big heart with clear lungs and low pressure or muffled sounds: urgent echo for pericardial effusion and senior review. ## Memory aid ABCDE: Alveolar oedema (bat wings), Kerley B lines, Cardiomegaly, Dilated upper-lobe vessels, Effusions. ## Test yourself Think of the answer, then tap the question to see it. ## Why should cardiomegaly not be diagnosed on an AP film? The heart sits far from the detector and the beam diverges, so an AP film magnifies it; a normal size on AP, though, is reliable. ## What are Kerley B lines? Short horizontal lines at the lung bases that reach the pleura: interlobular septa thickened by fluid, a sign of interstitial oedema. ## In what order do the X-ray signs of rising left atrial pressure appear? Upper-lobe venous diversion, then interstitial oedema (Kerley B lines, cuffing, thick fissures), then alveolar oedema in a bat-wing pattern. ## Which X-ray features favour ARDS over cardiogenic pulmonary oedema? Normal heart size, no septal lines or upper-lobe diversion, patchy peripheral opacity and few or no effusions. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/radiology/cardiomegaly-and-pulmonary-oedema-on-the-chest-x-ray/) ## Connections ## Related 7 - [Is this chest X-ray good enough? Projection, rotation, inspiration and exposure](https://durgical.com/en/radiology/is-this-chest-x-ray-good-enough-projection-rotation-inspiration-and-exposure/) - [Reading a chest X-ray step by step](https://durgical.com/en/radiology/reading-a-chest-x-ray-step-by-step/) - [Pleural effusion on the chest X-ray](https://durgical.com/en/radiology/pleural-effusion-on-the-chest-x-ray/) - [Consolidation and air bronchograms](https://durgical.com/en/radiology/consolidation-and-air-bronchograms/) - [Interstitial patterns: lines, nodules and honeycombing](https://durgical.com/en/radiology/interstitial-patterns-lines-nodules-and-honeycombing/) - [Lung ultrasound: A-lines, B-lines and lung sliding](https://durgical.com/en/radiology/lung-ultrasound-a-lines-b-lines-and-lung-sliding/) - [Focused cardiac ultrasound: effusion, function and the IVC](https://durgical.com/en/radiology/focused-cardiac-ultrasound-effusion-function-and-the-ivc/) ## Related conditions 1 - [Heart failure](https://durgical.com/en/conditions/heart-failure/) [← All of radiology](https://durgical.com/en/radiology/) Educational content; it does not replace a radiologist's report and is not a clinical instruction. Each study is ordered on the patient's assessment and your institution's protocols. Sources: [Cardiomegaly](https://www.ncbi.nlm.nih.gov/books/NBK542296/) (StatPearls (NCBI Bookshelf), 2022); [Pulmonary Edema](https://www.ncbi.nlm.nih.gov/books/NBK557611/) (StatPearls (NCBI Bookshelf), 2023); [Cardiogenic Pulmonary Edema](https://www.ncbi.nlm.nih.gov/books/NBK544260/) (StatPearls (NCBI Bookshelf), 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/radiology/cardiomegaly-and-pulmonary-oedema-on-the-chest-x-ray/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/radiology/cardiomegaly-and-pulmonary-oedema-on-the-chest-x-ray/