Which type of pulmonary edema is characterized by pneumonia, injury to alveolar septa, increased permeability, and pulmonary pressure normal?

• A. Microvascular
• B. Hemodynamic
• C. Osmotic
• D. Lymphatic

Answer: (A)

The main concept is noncardiogenic pulmonary edema caused by increased capillary permeability. When the alveolar septa are injured, as in pneumonia or inflammatory damage, the alveolar–capillary barrier becomes leaky. This lets protein-rich fluid flood the interstitium and alveoli, producing edema without a rise in hydrostatic pressure. That’s why pulmonary pressure can remain normal—the problem isn’t the heart pushing more fluid into the lungs, but the barrier itself allowing leakage.

This permeability edema is contrasted with edema driven by high hydrostatic pressure from left-heart failure (hemodynamic edema), where the capillary pressures are elevated and the fluid is more transudative with lower protein content. Osmotic edema would stem from low plasma oncotic pressure, and lymphatic edema from impaired drainage; neither is described by pneumonia-induced alveolar-septal injury with normal pressure.