What characterizes pitting edema?

Pitting edema is characterized by fluid accumulation in the interstitial spaces, which occurs when excess fluid builds up in tissues. The defining feature of this condition is that when pressure is applied to the swollen area, it leaves a temporary indentation or "pit" in the skin where the fluid has accumulated. This happens because the volume of fluid that has built up in the tissue can be displaced by pressure, allowing for a visible indentation.

This phenomenon typically occurs in conditions such as heart failure or kidney disease, where fluid retention takes place. The ability of the skin to rebound and fill back out after pressure is applied is what distinguishes pitting edema from other forms of edema that might not leave an indent.

While fluid accumulation in the chest and in extremities can occur in various forms of edema, they do not define pitting edema specifically. Non-pitting edema, in contrast, does not result in an indentation when pressure is applied, making the difference clear. Thus, the key characteristic of pitting edema is the indentation left behind, indicating how the fluid interacts with the surrounding tissues.