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Key Clinical Questions
What are the different types of plain chest radiographs and when would you order them?
What are the limitations of the anteroposterior (AP) film?
How does the chest radiography differentiate between different types of pneumonia from atelectasis?
What are the radiographic changes you should look for when considering acute, potentially life-threatening causes of chest pain?
What radiographic abnormalities require follow-up?
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The majority of hospitalized patients routinely have chest radiographs on admission or prior to surgery. Chest radiographs provide a snapshot of the patient’s physiologic health and insights into a wide variety of systemic diseases. Chest radiographs have the highest yield when obtained to evaluate acute cardiopulmonary signs or symptoms, or to assess the possibility of a complication following a procedure. Chest x-rays are also used to monitor critical illness in the intensive care unit (ICU), response to therapy as in congestive heart failure or pneumonia, and stability of pulmonary nodules.
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The clinician can minimize unnecessary test ordering and delays in diagnosis by recognizing the indications for different types of radiographs and their limitations. Table 114-1 summarizes the different types of chest projections, indications, and technical considerations. A posteroanterior (PA) radiograph provides more information than an anteroposterior (AP) projection. Due to magnification based on distance from the image data collector or film, the heart will appear larger on bedside AP chest radiographs and also in obese individuals. Hence, an AP image may suggest heart failure (upper lobe diversion, cardiomegaly, wide mediastinum, and high hemidiaphragms) in patients without fluid overload and significant pulmonary pathology may not be obscured. An AP film is also more likely to miss a small pneumothorax due to anterior collection of air, and diffuse shadowing may signify either poor inspiration or a posterior pleural effusion. Therefore, a PA radiograph may be required for more definitive diagnosis and is the preferred initial study. However, the patient must be able to cooperate and be clinically stable in order to be transported to another area in the hospital for acquisition of a posteroanterior radiograph. Although the standard chest radiograph may provide information about the overall health of the bones, special views should be obtained to properly assess the thoracic spine and shoulder joints in cases of trauma or infection. Rib fractures in particular may indicate more severe pulmonary injury than what is readily apparent from the plain film.
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