Which chest pathology shows very black lungs on imaging due to air trapping?

The presence of very black lungs on imaging due to air trapping is characteristic of emphysema. This condition is a form of chronic obstructive pulmonary disease (COPD) and involves the destruction of the alveolar walls, leading to enlarged air spaces and less elastic recoil in the lungs. As a result, air gets trapped during expiration, causing hyperinflation of the lungs.

On imaging, this hyperinflation manifests as increased radiolucency; hence, the lungs appear very black. The loss of lung tissue and the changes in the airways contribute to poor ventilation, exacerbating the appearance of blackness on X-rays or CT scans.

In contrast, bronchiectasis typically shows dilated airways but not the same degree of overall blackness due to air trapping. Pneumonia would present with areas of opacity due to consolidation, while asthma may result in transient hyperinflation during exacerbations but does not usually lead to the significant air trapping seen in emphysema on chronic imaging.

Thus, emphysema is correctly associated with the described imaging findings of very black lungs due to the nature of air trapping and lung hyperinflation.