Atelectasis can be characterized by which of the following terms?

Atelectasis refers to the collapse of part or all of a lung, leading to reduced gas exchange in the affected area. The term "crowded air bronchogram" specifically pertains to atelectasis because it describes a radiological finding where the airways become visible on imaging due to the surrounding lung tissues being dense or collapsed. In atelectasis, the normal air-filled alveoli are collapsed, causing the adjacent airways to appear more prominent as they are not surrounded by air and instead are surrounded by fluid or consolidated tissue.

The other terms relate to different conditions. "Fluffy infiltrate" often describes a pattern seen in pulmonary edema or infection but is not specific to atelectasis. "Ground glass appearance" typically reflects partial filling of air spaces and is seen in conditions like interstitial lung disease or viral pneumonia, rather than atelectasis. "Cavity formation" suggests the presence of an air-filled space within a consolidation, which can occur in infections like tuberculosis, but is not characteristic of atelectasis, where the lung volume is reduced rather than forming new spaces. Thus, "crowded air bronchogram" accurately illustrates the radiologic result of atelectasis.