This is the answer page to Case 4 from the page titled What is the Value of the Lateral Chest Projection?

• What is the Value of the Lateral Chest Projection?
• Patterns of Consolidation
• Patterns of Consolidation- LUL
• Lung Anatomy
• Paediatric Chest Radiography Positioning Aids

Unlabelled

The child is in an AP sitting position with a 15 degree wedge sponge behind his/her chest The image is taken with a CR system 8 posterior ribs are demonstrated. The child is in a slightly lordotic position The patient is not significantly rotated although the appearance of the right clavicle suggests the the child's right shoulder is positioned forward see below for labelled image

There are airbronchogram lines (arrowed) demonstrated behind the left heart shadow suggesting left lower lobe (LLL) consolidation. These lines are caused by airspace (alveolar) opacity in the LLL associated with a LLL infection (pneumonia) This is an example of silhouette sign

Lateral

The lateral projection was produced with the child in an erect sitting position with a 15 degree wedge sponge behind the child's chest. The child's soft tissues can be seen posteriorly to pucker up over the top of the 15 degree sponge.

The right hemidiaphragm is demonstrated (black arrow) The left hemidiaphragm is demonstrated partially (white arrow) and becomes obscured posteriorly. There is abnormal opacity overlying the lower thoracic spine region (grey arrows)

Discussion

This child has a left lower lobe consolidation which is likely to represent an acute pneumonia. The significant clue on the AP projection image is the presence of airbronchogram lines behind the heart. Whilst this condition can be diagnosed from the AP sitting projection by any person with skills in image interpretation, a less skilled observer could easily have missed this finding if a lateral projection image was not available. This is the sort of patient that turns up to the Emergency Department three days later in a considerably worse state than they presented the first time.

The pneumonitis is much easier to diagnose on the lateral projection image. There is abnormal posterior basal opacity with a silhouette sign involving the left hemidiaphragm. Another significant clue is that the thoracic spine should not appear lighter as you look from top to bottom- if anything, it should appear slightly darker as you look down the spine (until you reach diaphragm)

If this was your patient, would they have gone home with an undiagnosed left lower lobe pneumonia?

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