What is edema?

• A. Swelling due to fluid moving into the interstitial space.
• B. Increase in blood pressure within arteries.
• C. Infection of tissue causing redness.
• D. Fluid loss from the interstitial space.

Answer: (A)

Edema is swelling caused by excess fluid collecting in the interstitial space, the area between cells in tissues. This happens when fluid moves out of the blood vessels into the surrounding tissue faster than it can be drained, or when lymphatic drainage is impaired. That description directly captures edema’s defining feature: fluid accumulation in the interstitial space, leading to puffiness or swelling.

The other ideas describe different phenomena: higher arterial pressure relates to hypertension, not the tissue swelling from fluid accumulation; infection with redness points to inflammation, which can involve edema but is not the definition itself; and fluid loss from the interstitial space would reduce interstitial fluid, not cause edema.