Chest X-Ray

 

• CXR interpretation

  Mnemonic: ID RIP A-H

  ID:

  • Who is it of, and when was it taken?
  • Is it AP or PA? Image usually taken on inspiration with X-ray source behind i.e. postero-anterior (PA) view. In emergency situations, a mobile anterio-posterior (AP) view may be taken.

  Quality of X-ray, RIP:

  • Rotation of patient: are the clavicles symmetrical?
  • Inspiration: should see 5-7 ribs AP, 10 PA.
  • Penetration: should be able to see vertebral bodies.
  • Also comment if it's an adequate film in terms of containing the whole thorax.

  Airway:

  • Is it central?

  Bones:

  • Any fractures, mainly of the ribs. However, CXR not that sensitive for rib fractures.

  Cardiac size:

  • >50% across on a PA CXR suggests cardiomegaly. Hard to assess on AP.
  • Also note if the heart borders are clear, with fuzziness suggesting consolidation.

  Diaphragm:

  • Should be rounded. Flattened in hyperinflation.
  • Right should be slightly higher than left due to the liver.
  • Blurring of costophrenic angles suggests effusion or consolidation.
  • Air underneath suggests pneumoperitoneum e.g. from bowel perforation.

  Extra-pleural tissue:

  • Assess the soft tissue around the lungs.

  Fields of lung:

  • Tempting to jump here first, as it's the main focus, but good to take a stepwise approach before getting here.
  • Note their size (equal?), clarity (any white stuff?), and if lung markings (vessels) are visible to the edge.
  • Anatomical positions: right middle lobe at right heart border, left upper lobe at left heart border, right lower lobe at right hemidiaphragm, left lower lobe at left hemidiaphragm.
  • Say 'zones' – upper, middle, lower – not 'lobes' – and say 'hemithorax' not 'lung'. However, in the conclusion can talk about "most likely consistent with a X lobe pneumonia" etc.
  • Colour changes: opacification (whiteness), shadowing (slight whiteness), meniscus (curved fluid level).
  • There are 4 radiographic densities: air, fat, water/soft tissue, and bone. A border is only seen at an interface of 2 densities e.g. heart (soft tissue) and lung (air), with this 'silhouette' lost if air in the lung is replaced by consolidation.

  Gastric bubble:

  • Black spot below left diaphragm is normal.

  Hardware:

  • Any pacemakers or central lines?

• CXR findings in pleural effusion

  • Opacification with a curved upper edge (meniscus), pooled in bottom of lung and obscuring the costophrenic angle.
  • If very large: opacification of whole hemithorax and shift of (lower) mediastinum away from it.

• CXR findings in pneumothorax

  • Black area around the lung, with lung marking not going to the edge.
  • Tension pneumothorax: (upper) mediastinum (especially the trachea) shifts away from it.

• Discrete lesions on CXR

  Small lesions:

  • Often non-significant (e.g. calcified node), especially in the absence of clinical findings.

  Causes of lesions >3 cm:

  • Lung cancer.
  • Mets: multiple shadows.
  • Abscess or hydatid cysts: contain meniscus.
  • Cavitation e.g. tuberculoma: no fluid level. May contain calcification within lesion.
  • Rheumatic nodules.

• CXR findings in pneumonia

  General:

  • Consolidation: opacification of affected lobe(s) from pus-filled alveoli, with the air bronchogram sign i.e. bronchi appearing dark against opacification.
  • May also see lobar collapse, effusion, and/or abscess.

  Findings by lobe:

  • Lower lobe pneumonia: costo-phrenic angle may be obscured.
  • Right middle-lobe pneumonia: right heart border obscured.
  • Lingula pneumonia (inferior projection of left upper lobe): left heart border obscured.

• CXR findings in lobar collapse

  • Opacification of whole lobe due to loss of patent airways. May see clear borders of lobe. However, no air bronchograms as seen in pneumonia.
  • Trachea and mediastinum shift towards it.
  • ↓Vessel count.
  • Raised hemidiaphragm.
  • Crowding of ribs.

• CXR findings in heart failure

  ABCDE:

  • Alveolar oedema: sign of interstitial oedema.
  • Kerley B lines: sign of fluid in lung fissures.
  • Cardiomegaly: >50% across on a PA CXR.
  • Dilated upper lobe vessels.
  • Pleural Effusion.