In this article, we focus on the interpretation of a CXR. Have a low threshold to request one as they provide a lot of information with minimal radiation. Typically, if the patient is unwell enough to require admission, then the benefits of CXR outweigh the risks.

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Common scenarios to order a CXR

• Any suspicion of acute/chronic lung pathology (cancer, infection, oedema, effusion)
• Deteriorating patients
• Confirmation of NGT placement (this should ideally be done within working hours)
• Post interventions e.g. central line, chest drain or pacemaker (to rule out pneumothorax)

Always interpret a chest x-ray with an appreciation of the patient’s clinical assessment. It is difficult to differentiate consolidation from shadowing of pulmonary oedema on CXR but usually much easier in real life.

When to do a portable CXR?

If they are a deteriorating patient or you feel the patient may not be stable enough to be “outside” of nursing/medical care for 30 minutes – consider a portable chest x-ray. There is less medical equipment & medications down in the department should they deteriorate further. However, during a portable CXR, often the A&E queues will build as the radiographer has to leave the department.

Interpretation

• Confirm Details
  • Check patient details (name/DOB/hospital number)
  • Check the date and time of x-ray
  • Check if the patient has had previous x-rays (useful for comparison)
• Assess image quality (Rotation, inspiration, penetration or “RIP”)
  • Rotation – Make sure the spinous process is in equidistant to the medial of both clavicles
  • Inspiration – 5-6 anterior ribs should be visible
  • Penetration- check if the spine is visible behind the heart – ensuring good penetration
  • Check if the x-ray is PA or AP, is it a portable x-ray? Is it an erect x-ray?

• State any obvious findings
• Approach the chest x-ray systematically (ABCDE)

Airway

Check the trachea is central. If it is deviated – is it deviated away or towards the affected lung? Check hilar regions as well.

Breathing

Assess the lung fields. Divide the lungs into 3 zones and inspect the lung markings are present in each zone. Check if each lung is symmetrical with the other. Inspect the pleura as well.

Once again use the clinical context (raised JVP/peripheral oedema vs productive cough/raised inflammatory markers)

Cardiac

In a PA film, assess the cardiothoracic ratio where above 0.5 suggests cardiomegaly

Use the cardiac & diaphragmatic borders to ensure you don’t miss disease processes (but also to locate the lobe that might be affected). Lower lobe disease obscures the diaphragms whereas lingula or right middle lobe disease obscures the left and right cardiac borders respectively

Diaphragms

The right diaphragm is higher due to the liver & below the left, the stomach may have some gas bubbles. They may be flattened in obstructive airway disease such as COPD

Look for free gas under the diaphragm. Whilst bowel loops positioned between the liver & diaphragm could falsely show free air (Chilaiditi’s sign) this is rare & so assume perforation and discuss with seniors

Assess the costophrenic angles which might be obscured in pleural effusion (look for a meniscus) or consolidation 

• Everything else: mediastinum, bones, soft tissues & foreign tubes & devices

Written by Dr Zereda Zulkeefli (F2)
Checked by Dr Serena Virdi (ST1 Radiology)
Reviewed by Dr Vivienne Eze (ST4 Radiology)