## Pulmonary Edema of Drowning **Key Point:** The classic autopsy finding in drowning is pale, frothy, blood-stained fluid filling the airways and lungs — a hallmark of asphyxial death by drowning. ### Gross Pathology **Appearance:** - **Pale or whitish froth** — mixture of air, water, and mucus - **Blood-stained** — due to rupture of alveolar capillaries from increased intrapulmonary pressure - **Fills airways, bronchi, and alveoli** — extends into the trachea and mouth - **Bilateral and symmetric** — affects both lungs equally ### Mechanism of Formation 1. Water aspiration → disruption of surfactant 2. Increased capillary permeability → fluid transudation 3. Violent respiratory efforts during drowning → alveolar rupture and capillary hemorrhage 4. Foam formation → air mixed with fluid and mucus 5. **Pulmonary edema fluid** — characteristic pale, frothy appearance **High-Yield:** This frothy fluid is pathognomonic for drowning and is often visible at the nose and mouth ("pulmonary foam"). **Mnemonic: "FOAM"** — **F**rothy, **O**edematous, **A**irway-filling, **M**ucoid fluid. **Clinical Pearl:** The presence of diatoms (microscopic algae) in the lungs, bone marrow, or organs can confirm that the person was alive when submerged (diatom test), though this is less commonly used in modern practice.
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