A 28-year-old male is brought to the mortuary after being recovered from a river. External examination reveals frothy fluid at the mouth and nostrils, and the body appears bloated. The investigating officer requests the most specific investigation to confirm drowning as the cause of death. Which of the following is the investigation of choice?

Explanation

## Investigation of Choice in Drowning ### Diatom Test — Gold Standard **Key Point:** The diatom test is the most specific and confirmatory investigation for drowning. Diatoms are unicellular algae present in water bodies that enter the lungs and systemic circulation during the drowning process. ### Mechanism of Diatom Entry 1. Water enters the lungs during terminal gasping and aspiration 2. Diatoms are inhaled with aspirated water 3. They penetrate the alveolar wall and enter pulmonary capillaries 4. Diatoms are transported to distant organs (bone marrow, liver, kidneys, spleen) 5. The presence of diatoms in bone marrow is particularly significant as it indicates antemortem aspiration ### Why Diatom Test is Superior | Feature | Diatom Test | Other Investigations | |---------|-------------|---------------------| | **Specificity** | Highly specific (>90%) | Non-specific | | **Timing** | Confirms antemortem aspiration | Cannot differentiate antemortem vs postmortem | | **Presence in bone marrow** | Pathognomonic for drowning | N/A | | **False negatives** | Rare (diatom-poor water) | Common | | **Postmortem artifact** | Minimal | High | **High-Yield:** Diatom test is positive in ~80% of drowning cases. Negative result does not exclude drowning (diatom-poor water bodies may have low diatom content). **Clinical Pearl:** The presence of diatoms in bone marrow is more significant than in lungs because bone marrow is protected from postmortem contamination, making it the gold standard site for diatom examination. **Mnemonic:** **DIATOM** = **D**rowning **I**nvestigation **A**lternative **T**est **O**f **M**ortality ### Procedure 1. Tissue samples (lung, bone marrow, liver, kidney) are macerated 2. Treated with strong acid to dissolve organic matter 3. Diatoms are identified under light microscopy 4. Electron microscopy may be used for confirmation **Warning:** Diatoms can be found in postmortem water entry, but their presence in bone marrow specifically indicates antemortem aspiration and is pathognomonic for drowning.