Which statement is consistent with a microvascular cause of pulmonary edema?

• A. Pulmonary pressure is markedly elevated
• B. Is most likely caused by left heart failure
• C. Is associated with volume overload
• D. Is most likely caused by pneumonia

Answer: (D)

Microvascular pulmonary edema occurs when the capillary endothelium becomes leaky, so fluid escapes into the interstitium and alveoli due to increased permeability rather than because of high hydrostatic pressure. Inflammation from pneumonia triggers this permeability change, with cytokines and inflammatory cells injuring the capillary walls and promoting protein-rich fluid leakage into the air spaces. That inflammatory, permeability-driven mechanism fits microvascular edema best, making pneumonia a consistent cause.

Elevated pulmonary pressures point to edema from increased hydrostatic pressure (cardiogenic edema, such as left heart failure), not the microvascular permeability process. Volume overload similarly increases hydrostatic pressure and leads to cardiogenic-type edema.