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 on following page
  • 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

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!

Common cardiorespiratory conditions with multiple abnormalities

• COPD:
  • hyperinflation (>10 posterior ribs visible), flat hemi-diaphragms, decreased lung markings, black lesions (bullae), prominent hila
• Heart failure
  • (ABCDE): Alveolar shadowing (‘bat’s wings’ sign), B-lines (interstitial oedema), Cardiomegaly, Diversion of blood to upper lobe, Effusion