What is edema primarily characterized by?

Edema is primarily characterized by swelling due to excess fluid accumulation in the body tissues or cavities. This condition occurs when there is an imbalance between the hydrostatic pressure and osmotic pressure in the vessels, leading to fluid leaking into the surrounding tissues. It can manifest in various parts of the body, such as the legs, feet, and even the abdomen, depending on its underlying cause. The presence of excess fluid in the interstitial spaces results in the visible swelling that characterizes edema.

In contrast, excessive blood flow in the extremities can cause localized redness and warmth but does not define edema. Dehydration of the tissues would lead to the opposite effect, where tissues become dry and shriveled, showing a lack of fluid rather than an excess. Similarly, while pain in the extremities can accompany various conditions, it does not specifically indicate edema and is not a primary characteristic. Thus, the defining trait of edema is the swelling resulting from fluid retention.