System for looking at a CXR
Opening – say what it is! (e.g. this is a plain CXR!). Check it is the right patient, and the right date. Check it is also the right orientation. Check whether it is PA or AP. On an AP CXR the heart often appears larger than it is – so you can’t really comment on the heart size in these examples.
Check the exposure:
- In a normal exposure, you should be able to just see the vertebrae through the heart.
- If it is over exposed, it will be too dark
- If it is underexposed, it will generally be to pale
A – Airway – is it deviated?
B – Bones – look for fractures, notches, dislocations
C – Cardiac – is the heart enlarged (greater then ½ the width of the chest; the cardiothoracic ratio)
D – Diaphragm – is there air under the diaphragm, is the diaphragm raised? The phrenic nerve innervates the diaphragm. ‘C3, C4, C5 keeps the diaphragm alive’
E – Extrathoracic – air under the diaphragm, shoulder joints, air under the skin (surgical emphysema)
F – Fields (lung!) – any masses? Consolidation? Vascular markings? Collapse?
General Terms, hints and tips
- Hila – the left hilum is slightly higher than the right hilum.
- Gas – remember don’t be confused by gas in the stomach! So gas on the left is often normal, but gas under the right hemi diaphragm is not! Also, free gas in the abdomen usually (but not always) will go to the right first, because this is higher than the left.
- Blood vessels – are more extensive to the lower half of the lung than to the upper half. They sort of loop down from the heart like a droopy moustache.
- Free fluids – in the pleural space – i.e. pleural effusion – may or may not have a meniscus. The fluid (as long as it is erect CXR) will be at the bottom of the lung. If the pressure of the air is high, the meniscus may be flattened.
- If there isn’t a meniscus, you should question if the opacity is due to a fluid level or another cause.
- Ribs – remember you can see them anteriorly and posteriorly. Generally the posterior ribs will be more horizontal, and the anterior ribs will be more diagonally.
- Clavicle – to judge if the CXR is rotated or not, look at the distance between the central end of the clavicle, and the centre of the trachea. This distance should be equal on both sides
- Heart – to quickly estimate if the heart is enlarged – the diameter of the heart should be roughly less than ½ the width of the chest
- Aortic knob – this is the blob that the aortic arch makes on an x-ray
- Vascular markings – these should not be visible in the lateral 1/3 of the lung.
- Costophrenic recess – these will not be visible / will be filled in (opaque), in pleural effusion, and less commonly in consolidation.
- Diaphragm – the right is higher on a normal CXR due to the liver.
- Bronchial tree – the right is steeper than the left – due to the differing lobar structure. Inhaled foreigh object will usually fall down the right as it is steeper.
- Lung fissures – these can often be clearly seen if there is fluid – ie in pleural effusion.
- Transverse fissure – separates upper and middle lobes of the lung.
- Oblique fissure – separate the lower from the other two lobes – the upper and middle lobes are generally anterior, the lower lobe is generally posterior.
- In Right upper lobe collapse – the transverse fissure moves upwards
Fluid and air enclosed in the same space in CXR – e.g. pleural effusion + pneumothorax = hydropneumothorax. Other examples include a fluid filled stomach, and a fluid filled abscess.