CAMRT Radiography Practice Exam

On a chest x-ray, where should one look for evidence of a pleural effusion?

1. The apex of the lungs

2. The costophrenic angles and base of the lungs

3. The mediastinum

4. The diaphragm

The correct answer is: The costophrenic angles and base of the lungs

Looking for evidence of a pleural effusion on a chest x-ray is best done at the costophrenic angles and the base of the lungs. This area is particularly significant because pleural effusions tend to accumulate in the lowest portions of the thoracic cavity when the patient is upright. In a standard upright chest x-ray, the costophrenic angles are where fluid will become most evident, as fluid accumulates there due to gravity. Fluid will appear as blunting of the costophrenic angles, and if the effusion is large enough, it may also obscure the diaphragm or create a meniscus sign at the borders. Observing the base of the lungs is crucial as it helps radiologists determine the extent and significance of the effusion. The other locations mentioned in the choices do not provide the same visibility for pleural effusions. The apex of the lungs, the mediastinum, and the diaphragm can show various other conditions and abnormalities, but they are not the primary areas where pleural effusions manifest and can be clearly identified on chest x-rays.