Key points about pleural disease:
*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 effusion.
*If you miss a tension pnuemothorax, you risk a pt’s life!
If the lung edge measures more than 2 cm from the inner chest wall at the level of the hilum, 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.’
Key points to check for tracheal displacement:
- Check for rotation.
- Check central position.
- If displaced, try to determine if pushed (by increased pressure) or pulled (by loss of volume).
Key points to check around the hilum:
- The left hilum usually sits higher.
- Check size of hila.
- Check density.
- If displaced: pushed or pulled?
Lung zones, key points to look at:
- Compare left and right, and upper, middle and lower zones.
- Compare abnormality with rest of lung on same side.
- Whiter side is not always the abnormal side.
- Remember many lung diseases are bilateral and symmetrical.
Pleural effusion, differences in appearance between erect and supine:
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.
Note: Blunting of costophrenic angles usually caused by pleural effusion. Other causes include lung disease in the region of costophrenic angle and lung hyperexpansion.
Lobes, fissures and contours. Key points:
Two views are usually needed to determine the lobe involved.
Knowledge of the fissures and the diaphragm and heart contours can help determine where disease is located without the need for a lateral view.
Involvement of the right middle lobe may obscure the right heart border, and/or be limited by the horizontal fissure.
Diaphragmatic abnormalities, key points:
Check every x-ray for free intra-abdominal air under the diaphragm = pneumoperitoneum and a sign of bowel perforation.
An obscured hemidiaphragm may be due to adjacent lung disease.
An abnormal diaphagm position may indicate a serious pathology. Normal hemi-diaphragms for distinct dome-shaped contours against the adjacent lungs.
Right hemi-diaphragm usually lies slightly above the left.
Many causes of raised hemi-diaphragm: phrenic nerve damage, lung disease causing volume loss, congenital causes ed diaphragmatic hernia, or trauma.
Cardiomegaly and Heart failure, Key points:
Heart size should be assessed on every chest x-ray.
Enlarged if CTR > 50% on PA view.
If cardiomegaly is present, look for other signs of heart failure:
Pulmonary oedema, Septal lines/Kerley B lines, pleural effusions.
It may be possible to determine which chamber is enlarged.
An obscured heart border may indicate disease of the adjacent lung.
Septal (Kerley B) lines:
What causes them and what are they a sign of?
Kerley B lines:
are due to fluid accumulating between the secondary lobules of the lungs.
They are an elusive sign, but once spotted, pulmonary oedema is almost always the cause, especially in a patient with a cardiac history.
Occasionally sarcoidosis or lymphangitis carcinomatosa (both conditions that cause lymphatic obstruction).
Medialstinal widening, key points:
- A widened mediastinum is often due to technical factors - rotation, incomplete insp or AP view may enlarge width(and heart size).
- Genuine widening is usually due to a vascular abnormality or a mediastinal mass.
- A lateral view may help determine the location of a mass.
Soft tissue abnormalities, key points:
- Soft tissues may be mistaken for lung pathology
- Smooth black lines in the soft tissue may represent normal fat - but irregular black areas may represent surgical emphysema.
- Masectomy can change density in lungs.
Bone abnormalities, key points:
- Bone abnormalities need to be searched for carefully due to chest x-ray exposures not being optimal for bone.
- Chest radiography is not indicated for a suspected simple rib fracture (depends on centre)
- Malignant bone disease may manifest as either single or multiple lesions