Step 1: Pathogenesis of edema.
Edema is characterized by abnormal interstitial fluid accumulation, stemming from an imbalance in Starling forces and impaired lymphatic drainage.
Step 2: Etiology of edema.
1. Reduced plasma oncotic pressure (A): Observed in hypoalbuminemia resulting from malnutrition, nephrotic syndrome, or hepatic disease. This diminishes the reabsorption of fluid into capillaries.
2. Elevated capillary permeability (B): Occurs during inflammation, burns, or allergic reactions. Plasma proteins extravasate, augmenting fluid movement into tissues.
3. Impeded lymphatic drainage (D): Associated with filariasis, tumor compression, or lymph node excision. This hinders interstitial fluid clearance.
Step 3: Elimination of incorrect etiologies.
- (C) Increased plasma oncotic pressure: Contributes to fluid retention, not edema.
- (E) Decreased capillary permeability: Mitigates fluid leakage and does not cause edema.
Step 4: Determination.
The definitive causes of edema identified are A (Decreased plasma oncotic pressure), B (Increased capillary permeability), and D (Obstruction of lymphatic drainage).