Chest radiograph interpretation

Introduction

• Patient: name, DOB, hospital number, age, sex
• Previous films for comparison

Radiograph detail

• Date
• Type (anteroposterior or posteroanterior; erect or supine)
• Adequacy (RIPE)
  • Rotation: medial borders of clavicles should be equidistant from nearest spinous process
  • Inspiration: at least 5-6 anterior ribs should be visible above diaphragm
  • Picture area: lung apices and costodiaphragmatic recesses should be visible; scapulae should be out of the way
  • Exposure: vertebral bodies should be just visible through the lower part of the cardiac shadow (overexposure = too black; underexposure = too white)

Interpretation (ABCDE)

Briefly mention obvious abnormalities first

Airway

• Tracheal deviation (away from a pneumothorax or large effusion; towards a collapse)

Breathing

• Lung fields (compare in thirds) – see notes on analysing lung field abnormalities below
  • Air (pneumothorax)
  • Fluid (effusion)
  • Consolidation (e.g. due to infection)
  • Lobar collapse
  • Lesions (e.g. malignancy, abscesses)
• Pleura: look for pleural thickening (pleura not normally visible), and at lung borders for a pneumothorax
• Hilar region: look for lymphadenopathy, masses (malignancy), calcification, bilateral enlargement (sarcoidosis)

Circulation

• Heart size: should be <50% thorax diameter on PA film (cardiomegaly suggests heart failure)
• Heart position (may be displaced if there is lobar collapse or a large effusion)
• Heart shape and borders (right border = right atrium; left border = left ventricle)
• Great vessels: the aortic knuckle should be visible
• Mediastinal width: should be <8cm on PA film (widening may indicate aortic dissection)

Diaphragm

• Position and shape: right usually slightly higher due to liver (flat in COPD)
• Costophrenic angles (blunting indicates effusion)
• Air below diaphragm (abdominal viscus perforation)

Extra things

• Bones and joints: trace around ribs for fractures if clinically suspicious
• Soft tissues: look for swelling, subcutaneous air, masses, calcification of aorta

A patient presents to ED with chest pain and this trace. What would you do?

Interpretation management

Covered in OSCE Stations

To complete

• ‘To complete my analysis, I would examine previous films and ascertain the clinical history.’
• Summarise and suggest differentials

Analysing lung field abnormalities     

Background knowledge

• Four densities to note on a chest radiograph:
  • Bone
  • Soft tissue
  • Fat 
  • Air
• Wherever a density changes, a silhouette will be seen 
• Consolidated/unaffected lobes may be identified by determining if consolidation is contiguous with:
  • Diaphragm = lower lobes
  • Cardiac border = middle lobe (right)/lingula (left)

Describing the abnormality

• Density
  • Bone/soft tissue/fat/air density
• Uniform (i.e. same shade throughout) or non-uniform (i.e. blotchy)
• Radiograph position
  • Left or right
  • Zone
    • Upper (above 2^nd anterior rib)
    • Mid (between 2^nd and 4^th anterior rib)
    • Lower (lower than 4^th anterior rib)
• Anatomical position (lung parenchyma/pleural space)
• Size 
• Borders

For example: ‘There is a non-uniform soft tissue density in the left lower zone. Anatomically, this is in the lower lobe because the left hemi-diaphragm is not visible.’

Diagnosing the abnormality

• Consolidation
  • Non-uniform soft tissue density (i.e. blotchy white)
  • ‘Air bronchogram’ = visible bronchioles penetrating the consolidated areas (hence, it cannot be collapsed)
• Collapse
  • Uniform soft tissue density (i.e. pure white)
  • Affected lobe is smaller
  • Other structures move towards it into empty space (e.g. heart, other lung lobes, trachea)
• Effusion
  • Uniform soft tissue density (i.e. pure white)
  • Meniscus sign 
  • Fluid at lung bases if erect or along posterior thorax if supine
• Pneumothorax
  • Normal lung lobes, but they are partially deflated
  • Uniform air density (usually at top if erect)
  • Seen better on an expiration film
  • Look very carefully around pleura!

Test your knowledge

Interpret the following radiographs

This patient presented with breathlessness. Click the image to enlarge.

This patient presented with weight loss and night sweats. Click the image to enlarge.

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