Medical Term Glossary
Plain-language explanations of the medical terms that appear on CT, MRI and X-ray reports — what each one means, when it matters, and what to ask your doctor.
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Cardiomegaly
An enlarged heart on imaging. The heart looks bigger than expected when compared with the inside of the chest. It is a sign, not a diagnosis — the heart can grow because its walls have thickened from years of high blood pressure, because its chambers have stretched from extra workload, or because fluid has built up around it.
Also: big heart on scan, cardiac enlargement, dilated heart
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Consolidation (lung)
An area of lung where the tiny air sacs are filled with something other than air — usually fluid, pus, blood, or inflammatory cells. On imaging it looks denser and whiter than normal lung, and pneumonia is the most familiar cause. The pattern, location, and your symptoms together point to what is filling those air spaces.
Also: airspace disease, airspace opacity, dense lung opacity
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Pericardial effusion
Extra fluid sitting in the thin sac that surrounds the heart. A small amount is often harmless and very common. A larger volume can press on the heart and stop it filling properly, which is why the size on the report — and how quickly it built up — matters more than the finding itself.
Also: cardiac effusion, fluid around the heart, fluid in heart sac
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Pleural effusion
A build-up of fluid in the thin space between the lungs and the chest wall. Small amounts often cause no symptoms; larger collections can press on the lung and make breathing harder. The cause matters more than the fluid itself — infection, heart strain, and inflammation are the usual culprits.
Also: fluid around lung, fluid around the lungs, fluid in the chest
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Pneumothorax
Air that has leaked into the space between the lung and the inside of the chest wall, where there should be no air at all. The trapped air presses on the lung and stops it from inflating fully. Small leaks sometimes heal on their own, but larger ones need urgent treatment because they can make breathing difficult quickly.
Also: PTX, air around the lung, air leak in chest
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Pulmonary edema
Extra fluid leaking into the tiny air sacs and surrounding tissue of the lungs, making them heavy and less efficient at moving oxygen into the blood. It most often reflects strain on the left side of the heart, but inflammation, infection, kidney issues, and high altitudes can also cause it. Treatment focuses on the underlying reason.
Also: cardiogenic lung fluid, fluid in the lungs, lung congestion
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Pulmonary embolism
A blood clot that has travelled through the veins and lodged in one of the arteries supplying the lungs. Most start as a clot in a deep leg vein, break off, and ride the blood up through the heart before getting stuck. The size and location decide how serious it is, and the care team treats it promptly.
Also: PE, blood clot in the lung, clot in the lungs
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Pulmonary nodule
A small, rounded spot in the lung that stands out from the surrounding tissue. Most are smaller than a grape and most turn out to be harmless — leftover scars from old infections, tiny benign growths, or specks of inflammation. Size, shape, and whether it changes over time decide how closely it is watched.
Also: SPN, incidental lung nodule, lung nodule
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