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.
A
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Air bronchogram
A pattern where air-filled airways show up as dark branching lines against a brighter, denser background of lung. Normally these small airways blend in; they only stand out when the lung tissue around them fills with fluid or cells. It is a sign, not a disease, and most often points to ordinary causes like pneumonia.
Also: air bronchograms, air filled bronchi sign, branching air sign
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normal
Atelectasis
A small area of lung that has not fully inflated, so it looks denser than the air-filled tissue around it. It is one of the most common findings on a chest CT and is usually mild, temporary, and not a sign of disease on its own. The cause matters more than the finding itself.
Also: bibasilar atelectasis, collapsed lung, discoid atelectasis
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Bronchi
The branching airways that carry air from the windpipe into and through each lung, dividing again and again like tree branches into ever-smaller tubes. Reports comment on them when their walls look thickened, when they appear widened, or when something is blocking the flow of air through them.
Also: air tubes, airways, bronchial
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Bronchiectasis
Permanently widened airways in the lungs. The tubes that should taper smoothly as they branch deeper instead look stretched and baggy, which makes it harder to clear mucus and easier for infections to take hold. The damage itself does not reverse, but the symptoms it causes can usually be managed well with the right treatment.
Also: airway dilatation, bronchial dilatation, cylindrical bronchiectasis
C
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Cardiac silhouette
The outline of the heart as it appears on a chest image, seen as a solid shadow because the heart is full of blood and blocks the rays. Radiologists study its size and shape to judge whether the heart looks normal. The word describes the shadow, not a problem in itself.
Also: cardiac outline, cardiac shadow, heart outline
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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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Cardiothoracic ratio
A simple comparison of the heart's width to the width of the chest on a chest X-ray, written as a fraction or percentage. A value up to about half is generally considered normal. It is a rough screening number, easily thrown off by how the image was taken, not a precise measure of heart health.
Also: CT ratio chest x-ray, CTR, cardio-thoracic ratio
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Carina
The ridge at the point where the windpipe splits into the two main airways, one heading to each lung. It sits in the middle of the chest behind the breastbone. Radiologists use it as a fixed landmark, and check that nearby structures and any breathing tubes are sitting in the right place.
Also: airway fork, carina of trachea, tracheal bifurcation
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warning
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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Costophrenic angle
The sharp corner at the bottom edge of each lung, where the curved chest wall meets the dome of the breathing muscle below. On a normal scan this corner looks crisp and pointed. Radiologists watch it closely because it is one of the first places fluid or scarring tends to show up.
Also: CP angle, costophrenic angles, costophrenic recess
D
E
G
H
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Hemidiaphragm
One half of the dome-shaped breathing muscle that floors the chest, either the left or the right side. Each lung rests on its own half. Reports name it to specify which side they are describing, most often when one dome sits higher than the other or has an unusual outline.
Also: diaphragm half, hemi-diaphragm, hemidiaphragms
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Hilum
The central region on each side of the chest where the main blood vessels, the large airway, and lymph nodes enter and leave the lung. There is one on the left and one on the right. Reports comment on it when checking whether these structures look normal in size and density.
Also: hila, hilar, hilar region
K
L
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Lung apex
The rounded top of each lung, the highest part that reaches up behind the collarbone toward the base of the neck. There is one on each side. Reports look here for scarring, old infection, fluid, or small changes, since this corner can be subtle and easy to overlook.
Also: apex of the lung, apical, apices
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Lung markings
The fine network of branching lines seen spreading through the lungs on an image, mostly the small blood vessels and airways. Their presence and pattern are normal. Reports comment when they look increased, reduced, or crowded, since the pattern can shift with fluid, scarring, or trapped air.
Also: bronchovascular markings, interstitial markings, lung pattern
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Lymphadenopathy
Lymph nodes that look larger than normal on imaging. The body has hundreds of these small, bean-shaped filters scattered through the chest, neck, armpits, and elsewhere. They swell when they are doing their job — fighting infection — but can also enlarge from inflammation, autoimmune conditions, or, less commonly, cancer.
Also: enlarged lymph nodes, hilar lymphadenopathy, lymph node enlargement
M
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Mediastinal contour
The outline of the central zone of the chest, the strip between the two lungs that holds the heart, the great vessels, the windpipe, and lymph nodes. Radiologists trace its shape and width to check that this crowded middle region looks normal and nothing there is enlarged or pushed out of place.
Also: mediastinal borders, mediastinal margins, mediastinal outline
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Mediastinum
The central compartment of the chest, sitting between the two lungs. It contains the heart, the great blood vessels, the windpipe, the food pipe, lymph nodes, and several nerves. When a chest scan mentions this area, it is usually pointing at something sitting in that central region rather than in the lungs themselves.
Also: central chest compartment, central chest space, mediastinal area
P
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warning
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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urgent
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
Anything to do with the lungs. It is simply the medical adjective for 'relating to the lungs', from the Latin word for lung. On its own it carries no good or bad meaning — it just tells you which organ a finding involves. The noun attached to it, like nodule or artery, is what actually matters.
Also: lung, lung-related, of the lungs
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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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urgent
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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Pulmonary vasculature
The network of blood vessels inside the lungs that carries blood to pick up oxygen and return it to the heart. On a scan it forms the branching shadows fanning out from the centre. Reports describe whether these vessels look normal, fuller than usual, or sparse, since their fullness reflects pressure and flow.
Also: lung blood vessels, lung vasculature, pulmonary circulation
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Sternum
The breastbone — the flat, narrow bone running down the centre of your chest, the one you can feel in the middle of your ribcage. The ribs and collarbones attach to it, and it shields the heart and major vessels behind it. On a report it is usually just naming where in the front of the chest a finding sits.
Also: breast bone, breastbone, chest bone
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Superior vena cava
The large vein that drains oxygen-poor blood from the head, neck, arms, and upper chest back to the heart. Often shortened to SVC. It runs down the right side of the upper chest into the heart. Radiologists mention it when describing the vessels of the upper chest.
Also: SVC, great upper vein, main upper body vein
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