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. Common scenarios you might order a CXR include:
  • 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.

  • 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?
Normal CXR
  • 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.

    Tension Pneumothorax with Tracheal Deviation (pushed away from the affected lung)

    Bilateral hilar enlargement (sarcoidosis)

    • 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)

Bilateral consolidation

Pulmonary Oedema (AP portable film)

    • 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

Right middle lobe pneumonia

Left lower lobe pneumonia
    • 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 
Pneumoperitoneum as indicated by free air under the diaphragm

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

NG Tube
Rib fractures with a pneumothorax

Written by: Dr Zereda Zulkeefli (F2)

Checked by: Dr Serena Virdi (ST1 Radiology) 
Reviewed by Dr Vivienne Eze (ST4 Radiology)