Vitreous aspirated from an eye shows an unexpectedly high potassium concentration inconsistent with the degree of rigor and hypostasis present. Which technical error during collection BEST explains this finding?

• A Aspiration performed too slowly over several minutes
• B Use of a wide-bore needle causing globe collapse
• C Needle tip scraping the retina, drawing in retinal pigment epithelial cells ✓
• D Collection from the left eye instead of the right eye

Explanation

Potassium accumulates in vitreous mainly by leakage from retinal cells after death. If the needle tip touches or scrapes the retina, cellular potassium-rich material enters the aspirate and spuriously elevates the measured level, leading to overestimation of the postmortem interval. Laterality does not matter because both eyes behave similarly. Slow aspiration and using a fine needle are actually recommended precautions, so they do not explain the artefact.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.