In a drowning fatality examined postmortem, which combination of findings MOST strongly supports primary freshwater (not saltwater) drowning?

• A Hypernatraemia with haemoconcentration and elevated plasma magnesium
• B Diatoms in liver and bone marrow identical to diatoms recovered from the drowning site ✓
• C Haemodilution with hyponatraemia, decreased haematocrit, and elevated vitreous chloride > blood chloride differential
• D Absence of foam at mouth, dry lungs, and no water in stomach

Explanation

The diatom test (diatomological analysis) is the most reliable forensic indicator of drowning and the specific water body. Diatoms (siliceous microalgae) in the water are aspirated and, if the heart is still beating, circulate and lodge in internal organs (liver, kidney, bone marrow, brain). Recovery of diatoms from bone marrow and liver — protected from environmental contamination — that match diatoms from the suspect drowning site is strong evidence of vital immersion. Haematological changes (hyponatraemia/haemodilution) from freshwater aspiration may be present but are confounded by postmortem redistribution. Absence of foam is seen in dry drowning.

Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.