The Common Vein

Total lung collapse refers to the complete atelectasis of an entire lung, resulting in loss of aeration and significant volume reduction. It is caused by a variety of conditions, most commonly central airway obstruction or external compression. Importantly, tension pneumothorax can also result in total lung collapse due to the accumulation of air in the pleural space under pressure, compressing the lung and shifting mediastinal structures.

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Radiological Features

1. Chest X-Ray (CXR):
   • Complete Opacification:
     • The affected hemithorax appears completely opaque (obstructive or compressive collapse) or hyperlucent (tension pneumothorax).
   • Mediastinal Shift:
     • Toward the affected side: Seen in obstructive collapse.
     • Away from the affected side: Seen in tension pneumothorax.
   • Elevation of the Hemidiaphragm:
     • The diaphragm on the affected side is elevated in obstructive or compressive collapse.
   • Crowding of Ribs:
     • Narrow intercostal spaces on the side of obstructive collapse.
     • Widened intercostal spaces in tension pneumothorax due to pleural pressure.
   • Absence of Lung Markings:
     • In pneumothorax, there is no vascular lung pattern distal to the collapsed lung.
2. CT (High-Resolution CT):
   • Lung Collapse:
     • The lung appears as a dense, shrunken structure adjacent to the mediastinum or pleura.
   • Airway Obstruction:
     • Identification of the causative lesion in obstructive collapse (e.g., tumor, mucus plug, foreign body).
   • Tension Pneumothorax:
     • Hyperlucency in the pleural space with compression of the collapsed lung.
     • Mediastinal Shift Away from the Collapsed Lung: A hallmark feature.
     • Flattening or inversion of the ipsilateral hemidiaphragm.
   • Associated Features:
     • Pleural effusion or air-fluid levels (e.g., hydropneumothorax).

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Causes of Total Lung Collapse

1. Obstructive:
   • Endobronchial Tumors:
     • Primary lung cancer or metastatic disease.
   • Foreign Body:
     • Often in children.
   • Mucus Plug:
     • Common post-operatively or in conditions like asthma or cystic fibrosis.
2. Compression:
   • Pleural Effusion:
     • Large effusions leading to compressive atelectasis.
   • Mass Effect:
     • Mediastinal or chest wall tumors compressing the lung.
3. Tension Pneumothorax:
   • Accumulation of air under pressure in the pleural space.
   • Causes complete lung collapse by compressing the lung tissue.
   • Key Differentiating Features:
     • Mediastinal shift away from the affected side.
     • Severe flattening or inversion of the diaphragm.
     • Widened intercostal spaces on the affected side.
4. Trauma:
   • Rib fractures with lung puncture causing pneumothorax or hemothorax.

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Differential Diagnosis

• Large Pleural Effusion:
  • Uniform opacification but with a clear fluid level on upright imaging.
• Complete Pneumonia:
  • Diffuse consolidation without volume loss or mediastinal shift.
• Pulmonary Fibrosis:
  • Chronic condition with associated architectural distortion.

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Complications

• Tension Pneumothorax:
  • Life-threatening condition with hemodynamic compromise due to decreased venous return and cardiac output.
  • Requires immediate recognition and decompression.
• Hypoxemia:
  • Due to significant ventilation-perfusion mismatch.
• Secondary Infections:
  • Increased risk of pneumonia or abscess formation.

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Management

• Tension Pneumothorax:
  • Immediate needle decompression or chest tube placement.
• Obstructive Collapse:
  • Bronchoscopy to relieve obstruction (e.g., foreign body, mucus plug).
  • Biopsy for suspected malignancy.
• Compression Collapse:
  • Thoracentesis for pleural effusion.
  • Chest tube insertion for pneumothorax or hemothorax.

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Clinical Relevance

Including tension pneumothorax as a cause of total lung collapse highlights the importance of recognizing this life-threatening condition. Its radiological features, such as hyperlucency, mediastinal shift away from the collapsed lung, and widened intercostal spaces, make it distinct from obstructive and compressive causes. Early intervention is crucial to prevent fatal outcomes.

 

Radiologic Findings of Total Lung Collapse

1. Increased Opacity:
   • The collapsed lung becomes densely opaque on imaging, as the air is absorbed from the lung tissue and the remaining lung is composed primarily of soft tissue.
   • The entire hemithorax (one side of the chest) may appear more opaque than the unaffected side.
2. Mediastinal Shift:
   • Structures such as the heart, trachea, and mediastinum shift toward the collapsed lung due to the loss of volume on that side.
   • This shift can be prominent, especially in cases of complete lung atelectasis without compensatory hyperinflation on the contralateral side.
3. Elevation of the Hemidiaphragm:
   • The diaphragm on the side of the collapsed lung is pulled upward due to the decreased intrathoracic pressure on that side.
   • The hemidiaphragm may be noticeably higher than the one on the unaffected side.
4. Rib Space Narrowing:
   • There is narrowing of the intercostal spaces on the side of the collapse, as the chest wall is pulled inward by the loss of lung volume.
5. Silhouetting of Adjacent Structures:
   • The normal borders of structures like the heart, aorta, and hemidiaphragm may be obscured by the collapsed lung, which now occupies a smaller, dense space adjacent to these structures.
   • This finding can help in determining the location of the collapse and distinguishing it from other causes of increased opacity.
6. Compensatory Hyperinflation of the Opposite Lung:
   • The unaffected lung may appear hyperinflated, as it expands to fill some of the space left by the collapsed lung.
   • The expansion of the unaffected lung may include herniation across the midline into the space of the collapsed lung.
7. Crowding of Pulmonary Vessels and Bronchial Structures:
   • Bronchi and vessels within the collapsed lung appear crowded and may be displaced toward the hilum.
8. Bronchial Cutoff Sign (If Visible):
   • On CT or sometimes X-ray, the cause of the collapse, such as an obstructing tumor or mucus plug, may be visible as an abrupt cutoff in the bronchus.

Additional Findings on CT

CT imaging provides a clearer view and may show:

• Direct visualization of the obstruction if there is a mass, mucus plug, or foreign body.
• Collapsed lung tissue appearing as a dense, triangular or wedge-shaped opacity.
• Possible pleural effusion on the affected side, sometimes seen in cases of malignancy or infection.

Causes

Common causes of total lung collapse include:

• Endobronchial obstruction: Often due to a tumor, mucus plug, or foreign body in the main bronchus.
• Malignancy: Lung cancer can obstruct a major bronchus and is a common cause of total lung collapse in adults.
• Large pleural effusion or pneumothorax: Can indirectly cause lung collapse by compressing the lung from outside.

Summary

Total lung collapse results in a range of radiologic findings, primarily marked by increased opacity, mediastinal shift, elevation of the hemidiaphragm, narrowing of the rib spaces, and potential compensatory hyperinflation of the opposite lung. These findings are important to identify the presence and side of the collapse and suggest possible underlying causes that may require further evaluation.

Total Left  Lung Collapse
Tension Pneumothorax

 

Total Right Lung Collapse
Tension Hydrothorax

Whole Lung Atelectasis Due to Obstruction

Total Lung Compressive Atelectasis
Effusion

White Out of the CXR with Passive Compressive Atelectasis of the Left Lung

White Out of the CXR with Passive Compressive Atelectasis of the Left Lung
48 year-old male presents with a dyspnea. CXR shows a total white out of the left chest with pulmonary congestion. CT scan shows a large left pleural effusion with total atelectasis of the left lung. Incidental note is made of premature calcific coronary artery disease.
Ashley Davidoff MD TheCommonVein.net

Links and References

Chat GPT Radiological findings of total lung collapse aka total lung atelectasis