Patterns of Collapse

Introduction

For those with an interest in plain film image interpretation, patterns of collapse and consolidation are a very good place to start learning. Plain film chest interpretation is something of a holy grail. It might appear to be too difficult to contemplate, but as with most seemingly insurmountable tasks, if you take it a step at a time, you will succeed. This page provides an introduction to the topic.

Definition of Terms

Lung collapse refers to the loss of normal aeration and associated loss of volume(akin to deflating a balloon). The term consolidation when used by a radiologist, refers to the displacement of the air in the alveoli, smaller bronchii, and bronchioles, by exudate or oedematous fluid (Sutton, 1975, p325)

Anatomy

Patterns of collapse and consolidation can definitely not be learned without learning lung anatomy first.

Left Lung

The left lung has •1 fissure •2 lobes

Right Lung

The right lung has •2 fissures •3 lobes

Collapse

Plain Film Appearances of Lung Collapse

Radiological appearances common to all lobes are:

1. Reduced volume of the lobe

2. Opacity of the lobe

3. Displacement of fissures towards the opaque lobe

4. Vascular shadows in the remainder of the lung are more widely spread than normal

5. Hilar/mediastinal/diaphragmatic/tracheal displacement
Dixon and Dugdale, 1988,p25

Notes

1. Collapse and consolation can occur independently or together

2. Collapse can be partial or complete

3. It is often not clear to what extent the appearance is due to collapse or consolidation or both. The degrees of each are often unclear.

4. If a lobe is only partially collapsed and there is no accompanying consolidation, there may be no increase in opacity

5. In cases of pure collapse, only when the collapse is virtually complete will there be a significant increase in density of the affected lung

Hilar Displacement

Hilar displacement is an important indirect sign of lobar collapse. In most patients the left hilum is slightly higher than the right. Elevation of the hilum can be seen in cases of upper lobe collapse and depression of the hilum may be seen in lower lobe collapse. Middle lobe and lingular collapse do not affect the hilar positions.

Right Upper Lobe (RUL) Collapse

Right Middle Lobe (RML) Collapse

	increased opacity of lobe loss of visualisation of right heart border right hemidiaphragm visualisation unaffected airbronchogram (consolidation)
	increased opacity of lobe depression of horizontal fissure bowing of the inferior segment of the oblique fissure

Right Lower Lobe (RLL) Collapse

The PA view will show an area of opacity at the base of the right lung adjacent to the right heart border
The lateral view is usually definitive- there will be postero-inferior movement of the oblique fissure whilst maintaining the same slope The lower lobes collapse downward medially toward the spine and posteriorly

Left Upper Lobe (LUL) Collapse

The PA view will show an area of increased opacity in the left upper lobe with an ill-defined margin.	The PA view will shows an area of increased opacity in the left upper lobe with an ill-defined margin. Note the loss of the heart shadow/mediastinum and the mediastinal shift
The lateral view is usually definitive and often highly characteristic. As the LUL collapses, the fissure moves forward pivoting at its lowest point	The lateral view demonstrates the highly characteristic collapsed lobe which now lies parallel to the sternum

Left Lower Lobe (LLL) Collapse

The PA view will show a triangular area of increased opacity behind the left heart shadow. There may be loss of visualisation of the left hemi-diaphragm behind the heart The lower lobes collapse downward medially toward the spine and posteriorly
In the lateral view a triangular opacity will be seen at the base of the lung with a sharply defined anterior margin formed by the oblique fissure

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