What is a characteristic sign of edema?

Swelling of affected areas is a primary characteristic sign of edema. Edema occurs when excess fluid accumulates in the interstitial spaces of tissues, leading to noticeable swelling. This can happen for various reasons, including increased capillary permeability, reduced oncotic pressure, or obstruction of lymphatic drainage. The visible swelling is often most prominent in the extremities, such as the hands, feet, and legs, but can occur in any part of the body.

While inflammation of tissue can accompany edema, it is not a defining characteristic of edema itself, as edema can occur without inflammation due to other underlying conditions. Similarly, reduced blood flow might sometimes be associated with edema but is not a direct indicator of it. Increased oxygen levels in tissue would typically be unrelated to edema and does not indicate the accumulation of fluid. Therefore, the hallmark of edema is indeed the swelling that occurs in the affected areas.