Chest x-ray abnormalities
Pleural disease
The pleura only become visible when there is an abnormality present. Pleural abnormalities can be subtle and it is important to check carefully around the edge of each lung where pleural abnormalities are usually more easily seen. Some diseases of the pleura cause pleural thickening, and others lead to fluid or air gathering in the pleural spaces.
Pneumothorax
A pneumothorax forms when there is air trapped in the pleural space. This may occur spontaneously, or as a result of underlying lung disease. The most common cause is trauma, with laceration of the visceral pleura by a fractured rib.
If the lung edge measures more than 2cm from the inner chest wall at any point, it is said to be 'large.' If there is tracheal or mediastinal shift away from the pneumothorax, the pneumothorax is said to be under 'tension.' This is a medical emergency! Missing a tension pneumothorax may not only harm your patient, it is also the quickest way to fail the radiology OSCE at finals!
Key points
- The pleura and pleural spaces are only visible when abnormal
- There should be no visible space between the visceral and parietal pleura
- Check for pleural thickening and pleural effusions
- If you miss a tension pneumothorax you risk your patient's life - as well as your result at finals!
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Air in pleural space - Pneumothorax
- Visible pleural edge (blue line)
- Lung markings not visible beyond this edge
- Distance from lung edge to chest wall >2cm
- Healing rib fracture with callus (arrowhead)
Clinical information
- Fall from height - trauma to chest
Diagnosis
- Large left pneumothorax due to a rib fracture
- The trachea and mediastinal structures are not displaced so there is no 'tension'
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Pleural thickening
Pleural thickening is best seen at the lung edges where the pleura runs tangentially to the x-ray beam.
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Unilateral pleural thickening
- Peripheral shadowing on the right
- Loss of right lung volume
- Shadowing over the whole right lung due to circumferential pleural thickening
Clinical information
- History of asbestos exposure
Diagnosis
- Malignant mesothelioma - a disease caused by exposure to asbestos
Differential
- Empyema*
- Pleural metastases*
- Pleural effusions*
* Do not cause volume loss
Asbestos plaques
Calcified asbestos related pleural plaques have a characteristic appearance, and are generally considered to be benign. They are irregular, well-defined, and classically said to look like holly leaves.
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Asbestos related pleural plaques
- Bilateral well defined irregular shadows that are as dense as the bones
- Peripheral pleural thickening
Clinical information
- Chronic mild shortness of breath
- Retired dock worker with clear history of asbestos exposure
Diagnosis
- Bilateral calcified asbestos related pleural plaques
Pleural effusions
A pleural effusion is a collection of fluid in the pleural space. Fluid gathers in the lowest part of the chest, according to the patient's position. If the patient is upright when the x-ray is taken, a pleural effusion will obscure the costophrenic angle and hemidiaphragm. If a patient is supine a pleural effusion layers along the posterior aspect of the chest cavity and becomes difficult to see on a chest x-ray.
Pleural effusions
- The left lower zone is uniformly white
- At the top of this white area there is a concave surface - meniscus sign
- The left heart border, costophrenic angle and hemidiaphragm are obscured
- Slight blunting of the right costophrenic angle indicates a small pleural effusion on that side
Clinical information
- Life long smoker
- Weight loss and increasing shortness of breath
Diagnosis
- Large left pleural effusion
- Underlying bronchogenic carcinoma