Edema and Fluid Accumulation Causes

Edema

• Edema: Abnormal fluid accumulation in interstitial tissues (spaces between cells).
• Causes of Edema:
  • Increased hydrostatic pressure: Elevated pressure in capillaries forces fluid out (e.g., congestive heart failure, venous obstruction, inactivity).
  • Decreased osmotic pressure: Low plasma proteins (like albumin) reduce fluid reabsorption (e.g., liver cirrhosis, malnutrition, nephrotic syndrome).
  • Lymphatic blockage: Obstructed lymphatic vessels prevent fluid drainage (e.g., infection, tumors, lymph node removal).
  • Increased vascular permeability: Inflammation makes blood vessels leaky, allowing fluid and proteins to escape.
  • Sodium and water retention: Excess sodium or kidney problems lead to fluid retention; increases hydrostatic and decreases osmotic pressure.

Transudate vs. Exudate

• Transudate: Low-protein fluid (mainly water and electrolytes), clear/straw-colored, caused by increased hydrostatic or decreased osmotic pressure.
• Exudate: High-protein fluid, rich in cells/inflammatory mediators, cloudy/may contain pus, caused by increased vascular permeability (inflammation or infection).

Clinical Consequences of Edema

• Significance depends on location, extent, and duration.
• Location: Vital organ edema (lungs, brain) is life-threatening.
• Extent: Large volumes exert pressure, compressing tissues and impairing blood flow.
• Duration: Chronic edema can lead to tissue damage and organ dysfunction.

Thrombosis

• Thrombosis: Blood clot (thrombus) formation in blood vessels, obstructing blood flow.
• Virchow's Triad (risk factors):
  • Endothelial injury: Damaged vessel lining exposes collagen, triggering clotting.
  • Abnormal blood flow: Stasis (slow) or turbulence (irregular) promotes clot formation.
  • Hypercoagulability: Increased blood clotting tendency (e.g., genetic mutations, cancer, pregnancy, oral contraceptives).

Lines of Zahn

• Lines of Zahn: Alternating pale (platelets/fibrin) and dark (red blood cells) layers in a thrombus.
• Evidence of thrombus formation in flowing blood, distinguishing from postmortem clots.

Thrombus Outcomes

• Propagation: Thrombus growth, increasing vessel obstruction risk.
• Embolization: Thrombus fragment travels to another vessel, causing an embolism.
• Dissolution: Body's clot-dissolving process breaks down the thrombus.
• Organization & Recanalization: Thrombus replaced by scar tissue, potentially re-establishing blood flow.

Hemorrhage

• Hemorrhage: Blood escape from circulatory system.
• Types:
  • External: From open wounds or body openings.
  • Internal: Within tissues or body cavities.
  • Hematoma: Localized collection of clotted blood (e.g., trauma).
  • Petechiae: Tiny pinpoint hemorrhages.