What radiological term describes a fluid or solid filling the lung?

The term that describes a fluid or solid filling the lung is consolidation. In radiology, consolidation refers to the process where the lungs become filled with fluid, pus, blood, or other materials instead of air. This results in the lung tissue becoming more dense, which can be visualized on imaging studies such as chest X-rays or CT scans. On these images, areas of consolidation appear as opacified regions, meaning they do not allow as much light to pass through compared to normal, aerated lung tissue. This is commonly seen in various conditions, such as pneumonia, where the alveoli fill with fluid and inflammatory cells, indicating an underlying pathology affecting lung function.

This understanding is crucial for diagnosing respiratory conditions and determining appropriate treatments, as it directly relates to the presence of diseases that cause lung opacification.