Basic HRCT Patterns: Consolidation

Definition: Consolidation refers to lung opacity that completely obscures the vessels within a region.

 

How to Recognize Consolidation

This image shows complete opacification of most of the left upper lobe. Vessels are not visible in this area. When the bronchi remain aerated, they are seen as branching lucencies called air-bronchograms, which are present in this image.

This image represents infectious pneumonia, which is limited by the major fissure, resulting in a sharp border. The advancing anteromedial margin shows ground-glass opacity (see later).

HRCT is generally interpreted with the image displayed using "lung windows," as shown above, in which air is black, aerated lung is dark grey, and other structures are white.

Pulmonary consolidation has many causes, a common one being infectious pneumonia. Other causes include any process filling the air spaces with blood, fluid, or inflammatory cells. Alveolar collapse (atelectasis) also causes consolidation.

"Soft Tissue Windows" Defined

The same computer information from the image above can be displayed, as shown here, using "soft tissue windows," in which bone appears white; muscle, lymph nodes, and consolidated lung appear grey; and air and aerated lung appear black.

 

In this case, the patient received intravenous contrast, which results in a white appearance of the aorta, superior vena cava, the central left pulmonary artery, and branching pulmonary vessels on both sides. When contrast is used, vessels are often seen in consolidated lung when viewed on "soft tissue windows."

Slice of Lung with Lobar Consolidation

This slice of right lung shows consolidation of the middle lobe, which appears greyish compared to the surrounding non-consolidated lobes. The middle lobe was uniformly firm and maintained its shape, whereas the surrounding lung collapsed somewhat. The white nodules are metastatic carcinoma, and the pneumonia was the immediate cause of death.

When opacification of the lung appears spherical, the term mass, rather than consolidation, is often used, and the cause is commonly tumor.

 

Histology of Consolidation

Depending on the stage of the inflammatory response (early red hepatization or later grey hepatization), the alveolar spaces are filled with protein-rich fluid and red cells or PMNs and macrophages, respectively. Alveolar walls generally remain intact. Large airways are often free of exudate.

Most of the inflammatory cells here are PMNs or macrophages corresponding to a gross appearance of grey hepatization.

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