Define lymphedema.

• A. Swelling because of lymphatic vessel obstruction
• B. Swelling due to allergic reaction
• C. Fluid accumulation in the peritoneal cavity
• D. Generalized edema from malnutrition

Answer: (A)

Lymphedema is swelling that results from a failure of lymph drainage due to obstruction or damage to lymphatic vessels or nodes, causing lymph to accumulate in the interstitial spaces. The lymphatic system normally returns excess interstitial fluid, filtered through lymphatic vessels, back into the bloodstream; when drainage is blocked, fluid builds up, often in the limbs, and can become protein-rich and fibrotic over time. This distinguishes it from swelling caused by other processes: an allergic reaction involves inflammatory edema from increased vascular permeability; fluid in the peritoneal cavity is ascites; and generalized edema from malnutrition reflects low plasma oncotic pressure from hypoalbuminemia. The key idea is impaired lymph transport leading to interstitial fluid accumulation.