Which scenario would most likely contribute to edema?

• A. Decreased plasma albumin concentration
• B. Increased plasma albumin concentration
• C. Decreased hydrostatic pressure
• D. Decreased capillary permeability

Answer: (A)

Edema occurs when fluid moves out of the capillaries into the surrounding tissue rather than being reabsorbed back into the blood. This balance is governed largely by Starling forces, especially plasma oncotic pressure, which is the pulling force that keeps fluid inside the vessels and is largely provided by albumin. When plasma albumin concentration drops, oncotic pressure falls, so less fluid is pulled back into the capillaries. The result is more fluid leaving the vessels and accumulating in the interstitial space, leading to edema.

If albumin were increased, oncotic pressure would rise and fluid would stay more in the blood, reducing edema. Lower hydrostatic pressure would push less fluid out of the capillaries, also reducing edema, while lower capillary permeability would limit fluid leakage, again reducing edema. So the scenario that most promotes edema is decreased plasma albumin concentration.