Which finding best describes acute respiratory distress syndrome (ARDS)?

• A. Cardiogenic edema
• B. Chronic interstitial fibrosis
• C. Non-cardiogenic edema with bilateral infiltrates after insult
• D. Isolated lobar pneumonia

Answer: (C)

Acute respiratory distress syndrome presents as sudden, noncardiogenic pulmonary edema that causes hypoxemia and diffuse bilateral infiltrates on imaging after a known insult. The edema results from increased permeability of the alveolar-capillary membrane, not from heart failure, so left atrial pressures are not elevated. This is why the description emphasizes noncardiogenic edema with bilateral infiltrates occurring within a week of an insult such as sepsis, pneumonia, aspiration, trauma, or pancreatitis.

This helps distinguish ARDS from cardiogenic edema, which stems from cardiac dysfunction and often involves higher filling pressures and different imaging clues; it also separates ARDS from chronic interstitial fibrosis, which is a long-standing process, and from focal pneumonia, which would typically show a single area of consolidation rather than diffuse bilateral involvement.