A 28-year-old male is recovered from a river after 6 hours of submersion. On autopsy, the lungs are pale, voluminous, and frothy with fluid at the mouth and nostrils. The heart shows petechial hemorrhages. Which finding best distinguishes this as fresh water drowning rather than salt water drowning?

## Autopsy Findings in Fresh Water vs Salt Water Drowning ### Fresh Water Drowning Autopsy Features **Key Point:** Fresh water drowning produces characteristic **pulmonary edema** due to osmotic fluid shift INTO the alveoli: - **Pale, voluminous lungs** (often twice normal size) - **Frothy fluid** at mouth and nostrils (mixture of fluid and air) - Lungs appear waterlogged and spongy - Fluid is typically **clear to slightly blood-stained** - Brain edema is often present ### Salt Water Drowning Autopsy Features **Key Point:** Salt water drowning produces a different pattern: - Lungs are **congested and hemorrhagic** (darker, more blood-filled) - Pulmonary edema is present but **less voluminous** than in fresh water - Fluid is often **blood-stained or hemorrhagic** (due to hemoconcentration) - Lungs appear heavier and more consolidated - Cerebral edema is less common ### Comparative Autopsy Table | Finding | Fresh Water Drowning | Salt Water Drowning | | --- | --- | --- | | Lung appearance | Pale, voluminous, spongy | Congested, dark, hemorrhagic | | Pulmonary edema fluid | Clear, frothy | Blood-stained, hemorrhagic | | Lung weight | Markedly increased (>1500g each) | Moderately increased | | Froth at mouth/nose | Abundant, white/pink | Less abundant | | Brain edema | Marked | Mild | | Hemoconcentration | Absent | Present | | Serum sodium (postmortem) | Decreased | Increased | **High-Yield:** The **pale, voluminous, frothy lungs** are the hallmark of fresh water drowning and are the BEST autopsy discriminator. This reflects the osmotic influx of hypotonic fluid into the alveolar space. ### Clinical Pearl The "pulmonary edema" in fresh water drowning is so characteristic that it is sometimes called **"pulmonary edema of drowning"** because the volume of fluid is disproportionate to the degree of edema seen in other causes. The frothy appearance is due to the mixing of fluid with air during the drowning process. **Mnemonic:** **PALE FROTHY** = Fresh water (Pale lungs, Frothy edema). **DARK HEMORRHAGIC** = Salt water (Dark congested lungs, Hemorrhagic edema).