Imaging Case of the Week 93

These PA and lateral chest x-rays are from a 40 year old man with a history of fever and dyspnoea. What can you deduce from the x-rays?

chest x-ray PA

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chest x-ray lateral

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[peekaboo_link name=”Answer”]Answer[/peekaboo_link] [peekaboo_content name=”Answer”]

The PA view shows a retro-cardiac and left lower zone opacity, silhouetting the left dome of the diaphragm.

The lateral view shows a triangular opacity behind the heart, with a well-defined superior margin which is the displaced left oblique fissure.The increased density over the lower thoracic vertebra is due to associated consolidation.

Silhouette sign

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Left lower lobe collapse

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This patient has left lower lobe collapse consolidation. He was treated with intravenous antibiotics.

Silhouette sign is a loss of contour of the heart or diaphragm, used to localise a parenchymal process. A process involving the medial segment of the right middle lobe obscures the right heart border, a lingular process obscures the left heart border, and a basilar segment lower lobe process obscures the diaphragm.

While dealing with a patient with segmental lobar collapse, causes such as a mucus plug, endobroncheal lesion or a foreign body should be considered.

Any opacity noted on the chest x-ray in the ED needs a follow up film via GP. Bronchoalveolar carcinoma can present as a parenchymal process as opposed to a nodule.

A case of left lower lobe collapse can be found here:

Reference: Fundamentals of Diagnostic Radiology, Brant and Helms.