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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 2nd anterior rib)
      • Mid (between 2nd and 4th anterior rib)
      • Lower (lower than 4th 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
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CXR changes in heart failure
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