19 ANALYSIS: WHITE OUT

A white out: A frontal CXR shows homogeneous opacification of all or most of one hemithorax.

When assessing a white out it is essential to be aware of the possible causes (Table 19.1).

Table 19.1 Causes of a white out.

Common
image Large pleural effusion…with minimal or moderate secondary compression collapse of the underlying lung.
image Large pleural effusion…with major secondary compression collapse of the underlying lung.
image Collapse of the entire lung. Minimal or no pleural fluid.
image Previous pneumonectomy.
Uncommon Extensive pneumonia involving the entire lung.
Extremely uncommon Extensive tumour infiltration of the lung.
Extraordinarily rare Congenital absence of a lung.

WHITE OUT—ANALYSING THE CXR1-4

image The key to analysing a white out is determining whether the mediastinum is displaced. This requires assessment of the position of the heart and the position of the trachea.
image Mediastinum displaced to the opposite side = large effusion.
image Mediastinum displaced to the ipsilateral side = lung collapse.
image An occasional dilemma: a white out but: (a) there is no displacement of the mediastinum and (b) the trachea is central.
image The most likely cause: a large pleural effusion associated with or causing major collapse of the lung. The net effect is no displacement.
image Much less common: an extensive lobar pneumonia affecting all the lobes of the lung. An air bronchogram (p. 227) may be visible.
image Very rarely: extensive tumour infiltration of the entire lung.
image

Figure 19.2 White out. The mediastinum is displaced to the left and so is the trachea. Large right pleural effusion.

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Figure 19.3 White out. The mediastinum is central and so is the trachea. Large effusion with collapse of the underlying lung. The CT section shows the major compression collapse of the right lung caused by the large volume of fluid in the pleural space.

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Figure 19.4 White out. The mediastinum and trachea are displaced to the right side. Major collapse of the entire right lung.

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Figure 19.5 White out. The mediastinum and the trachea are displaced to the right side. Several of the underlying ribs are abnormal. A previous right pneumonectomy accounts for the white out.

Table 19.2 White out.

CXR findings Most likely cause
A
image Mediastinum displaced to the opposite side.
image Trachea central or deviated to the opposite side.
 Large pleural effusion with minimal secondary compression collapse of the underlying lung.
B*
image Mediastinum central.
image No tracheal deviation.
 Large effusion with major collapse of the underlying lung.
C
image Mediastinum displaced to the ipsilateral side.
image Trachea deviated to the same side.
 Collapse of the entire lung. Minimal or no pleural fluid.
D Features as for C above, and:
image Ribs missing/distorted.
 Pneumonectomy. The clinical history is conclusive.

* Exceptionally…these findings may be due to an extensive pneumonia affecting all the lobes of a lung, or to extensive tumour infiltration of the entire lung.

Answer to Fig. 19.1 on p. 264

image

Figure 19.1 Can you explain this white out? Answer on p. 266.

Analysis: Trachea and mediastinum are shifted to the right indicating a major loss of lung volume. But…always assess the bones. In this patient note the rib changes as well as the surgical clips.

Conclusion: A previous right pneumonectomy explains the white out.

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Figure 19.6 White out. A large left pleural effusion is displacing the mediastinum to the right.

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Figure 19.7 White out. The mediastinum and trachea are displaced to the right. Major collapse of the right lung.

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Figure 19.8 White out. The mediastinum is not displaced and the trachea is midline. Large left pleural effusion with major compression collapse of the left lung. The CT section confirms the effusion and the collapsed left lung.

REFERENCES

1. Ruskin JA, Gurney JW, Thorsen MK, et al. Detection of pleural effusions on supine chest radiographs. AJR. 1987;148:681-683.

2. Dee PM. The radiology of chest trauma. Radiol Clin North Am. 1992;30:291-306.

3. Leung AN, Muller NL, Miller RR. CT in differential diagnosis of diffuse pleural disease. AJR. 1990;154:487-492.

4. Kawashima A, Libshitz HI. Malignant pleural mesothelioma: CT manifestations in 50 cases. AJR. 1990;155:965-969.