Chest XRay Interpretation

Aka: Chest XRay Interpretation

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II. Imaging: General

  1. Confirm correct patient and views
    1. Patient name, date and time
    2. Left (L) Side marker should be on the side with heart prominence (or Dextrocardia)
  2. Determine film adeqaucy
    1. Alignment
      1. Note if patient is lordotic or kyphotic
    2. Rotation
      1. Spinous processes should be midway between clavicle heads
    3. Penetration
      1. Thoracic Spine should be visible through the heart
      2. Vessels should be visible
    4. Inspiratory film
      1. Diaphragm should be at or below the 10th rib (9 posterior ribs visible) on an adequate film

III. Imaging: Systematic Review

  1. General
    1. Compare findings from side to side
    2. Correlate findings on different views (e.g. PA with lateral view)
    3. Search the film in a consistent and systematic way
      1. Start centrally and work to lateral edges of the film
      2. Start with mediastinum and then to lungs, chest wall, diaphragm and upper Abdomen
  2. Soft tissues
    1. Evaluate for subcutaneous air, swelling
  3. Bones
    1. Evaluate clavicles, Vertebrae and ribs for Trauma, lesions
  4. Cardiovascular Structures and mediastinum
    1. Hilum is higher on the left
    2. Evaluate aorta, trachea and hilar masses
    3. Evaluate heart for cardiomegaly
  5. Diaphragm
    1. Hemidiaphragm is lower on the left (may be variable in older patients)
    2. Right hemidiaphragm sharply outlined
    3. Left hemidiaphragm sharply outlined lateral to cardiac apex
    4. Evaluate infradiaphragmatic areas for free air
  6. Pleural spaces
    1. Evaluate for Pneumothorax, Pleural Effusion or Hemothorax
  7. Lung parenchyma
    1. Evaluate for infiltrates, Nodules
    2. Localize any lesion on both lateral and AP films
  8. Lines and Tubes
    1. Endotracheal Tube should be above carina (Usually overlies 5-6th Vertebrae)
    2. Trace intravenous lines along entire course
    3. Trace Nasogastric Tubes along entire course

IV. Imaging: Findings that Help Define Lung Pathology

  1. Silhouette Sign
    1. Similar radiographic densities have indistinct margins
    2. Distinguish infiltrate, fluid or air
    3. Common regions of distorted margins
      1. Right heart border is obscured by a RML infiltrate
      2. Left heart border is obscured by a Left lingular infiltrate
      3. Right hemidiaphragm is obscured by a right lower lobe infiltrate
      4. Left hemidiaphram or descending aorta is obscured by a left lower lobe infiltrate
  2. Air Bronchogram
    1. Abnormal fluid filled alveoli (Pneumonia, blood or edema) or Atelectasis outline Bronchi
    2. Results in black branching appearance surrounded by white lung
    3. Air Bronchograms only occur in conditions affecting the lung

V. Imaging: Findings Mediastinum

  1. Widened Mediastinum (>6-8cm)
    1. See Widened Mediastinum
    2. Aortic Dissection
    3. Aortic Rupture
    4. Thoracic Aortic Aneurysm
    5. Thoracic Vertebral Fracture with Hematoma (high mechanism blunt Trauma)
    6. Other conditions include Mediastinal Mass or Lymphadenopathy, Hiatal Hernia
  2. Pneumomediastinum (with black air density vertical streaks)
    1. Esophageal Rupture
    2. Tracheal Laceration
    3. Pneumothorax
    4. Retroperitioneal air tracking via the mediastinum from the contiguous compartment
  3. Enlarged cardiac silhouette (>half the chest width)
    1. Cardiomegaly
    2. Congestive Heart Failure
    3. Cardiomyopathy
    4. Pericardial Effusion

VI. Imaging: Findings White Lungs

  1. See Straight Pulmonary Lines
  2. Pulmonary Infiltrates (distinguish between the 2 patterns)
    1. Interstitial Infiltrate (pulmonary vessels are visible with fuzzy margins, "Trees in fog")
      1. Interstitial Infiltrates occur within the connective tissue surrounding the air spaces
      2. Lung interstitial space is only visible in disease state (highlighted by fluid, fibrosis or tumor)
      3. Interstitial Infiltrates may be linear (e.g. Kerley B Lines), reticular (web-like) or nodular
    2. Alveolar Infiltrate (obscured pulmonary vessels)
      1. Infiltrates of fluid density within the air spaces (Bronchioles, alveoli) such as in Pneumonia
      2. Appears as white, opacified lung (Lung Consolidation)
  3. Atelectasis (Alveolar Collapse)
    1. See Atelectasis
    2. See Atelectasis on Chest XRay
    3. Obstructive Atelectasis (Bronchial Obstruction) from Lung Mass, mucus plugging, Foreign Body Aspiration
    4. Compression Atelectasis from Pneumothorax or Pleural Effusion
    5. Traction Atalectasis (lung scarring distorts alveoli) from chronic lung fibrosis or severe Pneumonia
    6. Relaxation Atelectasis (passive Atelectasis) from focal Splinting of respiratory Muscle (e.g. Rib Fractures)
  4. Cavitary Lung Lesion
    1. Dark air density center surrounded by a thick white soft tissue ring-like density
      1. Cavitary lesions may contain fluid with a distinct air-fluid level
    2. Causes include Lung Abscess, Fungal Pneumonia, Lung Granuloma (e.g. Tuberculosis), Lung tumor
  5. Pleural Effusion
    1. See Pleural Effusion
    2. See Pleural Effusion Causes
    3. Best seen on upright lateral Chest XRay or lateral decubitus film
  6. Congestive Heart Failure
    1. See Chest XRay in Congestive Heart Failure
    2. See Pulmonary Edema
    3. Cephalization of vascular prominence and hilar fullness
    4. Kerly B Lines (and other interstitial findings)
    5. Peribronchial cuffing
    6. Pleural Effusions
  7. Lung Nodules (and when >3 cm, Lung Masses)
    1. See Lung Nodule
    2. Round white fluid density lesions
  8. Hilar Adenopathy
    1. See Hilar Node Enlargement
  9. Azygos Vein
    1. radlungcxrazygusvein.jpg
    2. May be seen in the Chest XRay of up to 2% of patients (anatomical variant)
    3. Azygos vein is a normal vertical vessel paralleling the spine the upper right chest
      1. Drains the posterior chest into the superior vena cava
      2. May be more prominent in Fluid Overload or increased Right Atrial Pressure

VII. Imaging: Findings Black Lungs

  1. Pneumothorax
    1. See Pneumothorax Imaging
    2. Upright, expiratory PA Chest XRay with apical black cresent and absent lung markings
    3. Tension Pneumothorax may shift the mediastinum away from the Pneumothorax
  2. Emphysema
    1. Lung hyperinflation
    2. Diaphragm flattening
    3. Distal pulmonary vessel tapering
    4. Increased basilar markings in Chronic Bronchitis
  3. Pulmonary Embolism
    1. XRay excludes other Dyspnea Causes (e.g. Pneumothorax, Pneumonia)
    2. Consider Pulmonary Embolism in Acute Dyspnea, Hypoxemia and clear lungs on exam and XRay
    3. Nonspecific Chest XRay changes in 85%
      1. Elevated hemidiaphragm (50%)
      2. Pleural Effusion
      3. Plate-like Atelectasis
      4. Hampton's Hump (lung infarct)
        1. Peripheral wedge shaped infiltrate or opacity at the edge of the lateral pleura
        2. Pleural based infiltrate pointed towards hilum
      5. Westermark Sign
        1. Dilated proximal vessels with a distal cutoff
        2. Marked decreased vascularity distal to a large Pulmonary Embolism

VIII. Imaging: Findings Chest Wall

  1. Rib Fractures
    1. Chest XRay Test Sensitivity for Rib Fracture: 33-50% (compared with CT)
      1. However, Rib Fractures not seen on Chest XRay are typically not Clinically Significant
      2. Fractures are most common at the lateral aspect of the rib (weakest segment)
    2. Turn XRay on its side (use software rotation)
      1. Follow arch lines of both anterior and posterior aspects of the ribs
      2. Fracture lines are more evident in this view
    3. Evaluate for Rib Fracture related complications
      1. Pneumothorax (esp. with Rib Fractures 4-9, obtain expiratory upright PA film)
      2. Hemothorax
      3. Pulmonary Contusion
      4. Widened mediastinum
  2. Subcutaneous Emphysema
    1. Appears as dark streaks within subcutaneous soft tissue regions of the chest and neck
    2. Suggests Pneumothorax, Esophageal Rupture, Tracheal Laceration (or localized in skin Laceration)

IX. Imaging: Findings Diaphragm

  1. Diaphragmatic Rupture (left side in 90% of cases)
    1. Stomach or bowel appears in the left chest
    2. Nasogastric Tube curled in the left chest
    3. Mediastinum may be deviated toward the right side
    4. Differential diagnosis
      1. Elevated left hemidiaphragm
      2. Left loculated Pneumothorax
      3. Left subpulmonary Hematoma
  2. Hiatal Hernia
    1. Stomach fundus protrudes above the diaphragm (Herniated via the esophageal hiatus)
    2. Mediastinal air fluid level in the retrocardiac region (may be best visualized on lateral Chest XRay)
  3. Subdiaphragmatic free air
    1. Free air seen on upright PA Chest XRay
    2. Concerning for hollow viscus rupture

X. Resources

  1. LITFL: Chest XRay Interpretation
    1. https://lifeinthefastlane.com/investigations/cxr-interpretation/

XI. References

  1. Marini (1987) Respiratory Medicine, Williams & Wilkins
  2. Ouellette and Tetreault (2015) Clinical Radiology, Medmaster, Miami, p. 4-25

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