Which condition is characterized by swelling of the lungs?

Pulmonary edema is characterized by the accumulation of fluid in the lung tissues and alveoli, leading to swelling. This condition typically occurs when there is an imbalance in hydrostatic and oncotic pressures within the pulmonary circulation, which can result from heart failure, direct lung injury, or other medical conditions. The fluid buildup hampers gas exchange, causing difficulties in breathing and reduced oxygen levels in the blood.

While pneumonia, bronchitis, and aspiration pneumonia can also affect lung function, they primarily involve inflammation or infection of lung tissues rather than swelling due to fluid accumulation. Pneumonia involves the alveoli filling with pus or fluid due to infection, bronchitis is primarily the inflammation of the bronchial tubes, and aspiration pneumonia occurs when foreign substances enter the lungs but does not specifically denote swelling. Pulmonary edema distinctly refers to the condition where excessive fluid causes swelling in the lungs, which makes it the correct choice.