While examining a chest x-ray from an adult patient, an RT notes the presence of air bronchograms. Which of the following is the most likely cause?

Air bronchograms are a radiographic sign seen on chest X-rays, characterized by the visibility of air-filled bronchial tubes against a background of opaque alveoli. This phenomenon occurs when the lung tissue surrounding the bronchi is filled with fluid or other materials, allowing the air-filled bronchi to become distinct.

In the case of pneumonia, the lung parenchyma becomes consolidated due to infection, leading to inflammation and the accumulation of pulmonary infiltrates in the alveoli. This accumulation can obscure the surrounding lung tissue, making the bronchi more visible on a chest X-ray, hence producing air bronchograms. It is this classic finding that aids in diagnosing pneumonia, particularly when evaluating the extent and severity of the infection.

On the other hand, conditions such as pneumothorax, pleural effusion, or bronchiectasis do not exhibit air bronchograms in the same manner. Pneumothorax involves the presence of air in the pleural space, which would usually lead to a more expansive lung appearance on X-ray. A pleural effusion is the accumulation of fluid in the pleural space, which tends to obscure lung markings rather than reveal them. Bronchiectasis may show some changes in the bronchi themselves but typically does not