What condition is defined as pathological distention of tissues by gas or air?

The condition defined as pathological distention of tissues by gas or air is emphysema. This medical term specifically refers to a condition in which the air sacs (alveoli) in the lungs are damaged, leading to an enlargement of the air spaces and a reduction in the surface area available for gas exchange. The distention occurs due to the trapping of air that cannot be exhaled properly, which is a hallmark of emphysema.

In contrast, other options present different medical concerns: diplopia refers to double vision, empyema is an accumulation of pus in a body cavity, typically in the pleural space associated with infection, and dysuria is the term for painful or difficult urination. Each of these terms pertains to distinct conditions that do not involve the pathological distention of tissues by gas or air, making emphysema the accurate choice for this definition.