Back to: General X-ray eLearning
Look at the CT topogram below:
The entire left lung is completely white. When you see this, you have to make a decision – is it a push or pull pathology? In this case, is the left lung pathology pushing the mid-line structures towards the right side or is the left lung pathology pulling the mid-line structures towards itself.
In this example, you can see the left lung pathology pulling the mid-line structures towards itself (evident by the tracheal deviation). This would suggest that this pathology has reduce the left lung volume causing the right thorax to expand and move into the resultant void.
This is clearly seen in the coronal CT image below.
In the image above, the heart and mid-line structures have translated into the space normally occupied by the left lung. Therefore, the white opacity that you saw on the topogram is actually the heart shadow. This patient has had a left pneumonectomy. Therefore, there is no left lung. The right thorax and mediastinal structures have moved across to fill the void.
This translation also demonstrates a fundamental property of nature, moving from an area of high concentration to low concentration to achieve equilibrium. This property is evident in many sciences and helps in the radiology diagnosis.
Is it technique or pathology
Students should critique their image first before making a judgement on pathology. A wise radiologist once told me, “we cannot make real pathology look normal but we can make normal anatomy look like pathology”. Make sure you check your images for things like rotation, tilt and inappropriate image quality.
Referring to the image above. A student might believe that there is pathology in the right lung because the right heart border has an abnormal shape and looks more dense. However, there is gross patient rotation towards the right side causing the right throax and right heart border to elongate and the left thorax to foreshorten. This is a normal supine chest x-ray.
Thus, patient rotation can mimic pathology.
Push and pull pathologies
Common pathologies that pull structures towards itself
- radiation fibrosis (reduction in lung elasticity due to fibrosis = reduction in lung expansion = pulling towards itself)
- lung lobe collapse (there is a whole list of common appearances for each of the 5 lobe collapses available on the internet.)
Common pathologies that push structures away from itself
- pneumothoraces (both tension and simple)
- solid consolidation
- bullae
Of course no list is perfect and the lists above are by no means comprehensive. There are some pathologies that can cause either effect and it depends on its aetiology and physical manifestation. E.g. some lung masses can push or pull.