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Chest X-ray
A chest X-ray, commonly abbreviated CXR, is a projection radiograph (X-ray), taken by a radiographer, of the thorax which is used to diagnose problems with that area. The typical radiation dose to an adult from a chest x-ray is around 6 mrem.[1] Additional recommended knowledge
Problems identified through chest x-raysExamples of such problems include but are not limited to:
Chest X-Rays are among the most common films taken, being diagnostic of so many important problems. Features that are typically examined on a chest X-rayEvery doctor will have a different approach to examining chest X-rays. A commonly used mnemonic for what to look for on a chest X-ray is: It May Prove Quite Right (but) Stop And Be Certain How Lungs Appear:
Another approach is to examine first any major abnormality, and then "review areas":
ViewsTypical views
The most common view is the PA (posterior-anterior) and is frequently done with a left lateral view (so one can identify the location of abnormalities in 3-D space). PA views are generally preferred to AP views (which are often done with mobile/portable X-ray equipment), but much less convenient in the ICU setting or when a patient cannot otherwise leave their bed. PA views are preferred because the central shadow is better defined, the magnification of the heart is reduced, and less of the lungs obscured by the heart/pericardial sac. Additional views
AbnormalitiesNoduleA nodule is a discrete opacity in the lung which may be caused by:
There are a number of features that are helpful in suggesting the diagnosis:
If the nodules are multiple, the differential is then smaller:
CavitiesA cavity is a walled hollow structure within the lungs. Diagnosis is aided by noting:
The causes include:
Pleural abnormalitiesFluid in space between the lung and the chest wall is termed a pleural effusion. There needs to be at least 75ml of pleural fluid in order to blunt the costophrenic angle on the lateral chest X-ray, and 200ml on the posteroanterior chest X-ray. On a lateral decubitus, amounts as small as 5ml of fluid are possible. Pleural effusions typically have a meniscus visible on an erect chest X-ray, but loculated effusions (as occur with an empyema) may have a lenticular shape (the fluid making an obtuse angle with the chest wall). Pleural thickening may cause blunting of the costophrenic angle, but is distinguished from pleural fluid by the fact that is occurs as a linear shadow ascending vertically and clinging to the ribs. Diffuse shadowingThe differential for diffuse shadowing is very broad and can defeat even the most experienced radiologist. It is seldom possible to reach a diagnosis on the basis of the chest X-ray alone: high-resolution CT of the chest is usually required and sometimes a lung biopsy. The following features should be noted:
Pleural effusions may occur with cancer, sarcoid, connective tissue diseases and lymphangioleiomyomatosis. The presence of a pleural effusion argues against pneumocystis pneumonia.
LimitationsIt must be remembered that while the chest X-ray is a cheap and safe method of investigating diseases of the chest, there are a number of serious chest conditions that may be associated with a normal chest X-ray and other means of assessment may be necessary to make the diagnosis:
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chest_X-ray". A list of authors is available in Wikipedia. |