Atelectasis refers to lung collapse with loss of internal air, affecting parts of a lung or the entire lung, with subsegmental atelectasis being the most common. Causes include bronchogenic carcinoma, asthma, and foreign body aspiration, with specific chest X-ray features indicating collapse, such as tracheal displacement and increased density. Diagnosis requires assessing volume loss and the movement of surrounding structures, with lung cancer being the most common cause in adults.

1. Atelectasis

2. What does atelectasis mean?
• Lung collapse with loss of internal air
• Atelectasis can affect:
– a subunit of a lobe (subsegmental)
– a lobe
– or a whole lung
• Subsegmental atelectasis is most common

3. Causes of Lobar/Whole Lung Atelectasis
• Proximal stenosing bronchogenic carcinoma
• Asthma (mucus plugging)
• Inhaled foreign body
• Retention of secretions (e.g. postop)
• Endotracheal tube inserted too far

4. CXR Features of Lobar/Whole
Lung Atelectasis
• Ipsilateral tracheal displacement
• Increased density of collapsed lung tissue
• Ipsilateral mediastinal shift
• Elevation of the hemidiaphragm
• Herniation of the opposite lung across the
midline

5. Complete left lung collapse

6. Complete left lung collapse
Trachea deviated
to left
Heart shifted to
left
Opaque (white)
hemithorax,
caused by non-
aerated lung

7. Patterns of Lobar Collapse
• The left lung has 2 lobes (upper, lower), and
the right lung 3 lobes (upper, middle, and
lower)
• The collapse of each lobe has specific
appearances on a CXR
• Examples of each type of lobar collapse now
follow
• A revision of your lung anatomy now might
be helpful

8. Surface markings of the lobes
•The lingula is part of the left upper lobe
•Note that the lower lobes extend quite high – above the level of the carina

9. Right Upper Lobe Collapse

10. Examples of Lobar Atelectasis
• There now follows examples of each
type of lobar atelectasis.
• Some are difficult to recognise!
• For each one, look for volume loss (e.g.
ribs closer together), and movement of
other structures to occupy the space
created by the atelectasis.

11. Right Lower Lobe Collapse

12. Right Lower Lobe Collapse
The right lung has lost volume and the horizontal fissure is depressed
(red arrow)

13. Middle Lobe Collapse

14. Middle Lobe Collapse
The right heart border is blurred. Middle lobe collapse can be very
difficult to detect, and a lateral CXR can be helpful if in doubt (next slide)

15. Middle Lobe Collapse
Note the wedge shape on the lateral CXR. The horizontal fissure (arrow)
is depressed

16. Left Upper Lobe Collapse

17. R
Left Upper Lobe Collapse

18. Note loss of volume of the
left hemithorax and
generalised increased
density. The lung markings
still visible are those of the
lower lobe, which expands to
fill the space left by the
collapsed upper lobe
R
Left Upper Lobe Collapse

19. Left Lower Lobe Collapse

20. Left Lower Lobe Collapse
Note loss of left diaphragm contour medially, volume loss of the left hemithorax and
the retrocardiac straight line (representing the collapsed lower lobe)

21. Take Home Points
• The commonest cause of lobar / total
lung collapse in adults is lung cancer
• All patients with lobar or total lung
collapse need further assessment to
determine the underlying cause
• The CXR appearances of collapse vary
according to where the collapse is