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Special autopsy techniques: air embolism, pneumothorax, neck dissection

  • Procedure

Some findings disappear with a routine autopsy, so they must be suspected beforehand and looked for with a special technique or imaging.

Updated

What it is

A routine opening of the body can destroy the evidence of some causes of death. Air in the circulation (air embolism) and air in the pleural space (pneumothorax) escape as soon as the vessels or the chest are opened, and an ordinary neck dissection can create bleeding that looks like strangulation. So, when the history suggests them (a central venous line, endoscopy or surgery, diving, chest or neck injury, suspected strangulation), the examiner plans the technique before the first incision. Postmortem CT before the autopsy is the most sensitive way to show gas, but gas also forms through decomposition, so its origin must be interpreted with care. Layer-by-layer neck dissection in a bloodless field, and subcutaneous dissection of the back and limbs to find deep bruises, complete these techniques.

What to document

  • Which technique was used, why it was chosen and at what stage of the autopsy.
  • Imaging findings before the autopsy and the time since death when the scan was done.
  • Gas: site, approximate amount, whether samples were taken and the state of decomposition.
  • Neck: bleeding in each muscle layer, fractures of the hyoid or larynx and whether they show vital reaction.
  • Deep bruises found only by subcutaneous dissection, with site and size.
  • Limits: for example, a body already opened or decomposed, where the technique could not be applied.

How it is done

  1. Read the history and scene report: plan special techniques before any incision.
  2. If available, perform CT before the autopsy to show gas in vessels, heart chambers and pleural spaces.
  3. For pneumothorax, use imaging or the water test before the chest is opened, and record the side and the result.
  4. For air embolism, avoid letting air into vessels before looking; open the pericardium, fill it with water and puncture the right heart under water.
  5. If gas appears, aspirate it with a gas-tight syringe for chromatography and record which chambers contained it.
  6. Remove the brain and chest organs first; then dissect the neck muscles one layer at a time, from superficial to deep.
  7. Examine the hyoid bone and laryngeal cartilages in place and after removal; consider a posterior neck dissection.
  8. Dissect back, buttocks and limbs under the skin when restraint, beating or abuse is suspected.

Next step: what to do and document

  • When a death follows a central line, endoscopy, surgery, diving or chest injury, warn the examiner so the technique is planned.
  • Do not remove lines, tubes or drains placed during care: they show where air may have entered.
  • Report gas findings together with the degree of decomposition, and do not call it embolism without considering putrefaction.
  • In suspected strangulation, record that the neck was dissected last in a bloodless field.
  • State in the report when a technique was not possible and how that limits the conclusions.

Common mistakes

  • Letting air into the vessels during the dissection before looking for air embolism, which creates a false finding.
  • Opening the chest without first looking for pneumothorax.
  • Calling any intracardiac gas embolism in a decomposing body.
  • Dissecting the neck with the vessels full of blood and reading the resulting bleeding as strangulation.
  • Fracturing the hyoid bone during removal and reporting it as an injury.

Test yourself

Think of the answer, then tap the question to see it.

How is a pneumothorax shown at autopsy?

Before the chest is opened: by X-ray or postmortem CT, or by the water test, in which gas bubbles appear when the pleura is opened under water.

Why must air embolism be suspected before the autopsy starts?

Because a routine opening can let air into the vessels and create a false finding, or let the real gas escape; imaging and the technique are planned beforehand.

What finding on postmortem CT suggests that heart gas is not due to decomposition?

A large amount of gas in the right heart with little or no gas in the liver tissue; gas chromatography confirms the origin.

Why is the neck dissected layer by layer in a bloodless field?

To avoid bleeding caused by the dissection itself, which could be mistaken for the bruising of strangulation.

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Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.

Sources: The Minnesota Protocol on the Investigation of Potentially Unlawful Death (2016) (Office of the United Nations High Commissioner for Human Rights, 2017); Systemic air embolism complicating upper gastrointestinal endoscopy: a case report with post-mortem CT scan findings and review of literature (Forensic Sciences Research (Ali Z et al.), 2016); Modern post-mortem imaging: an update on recent developments (Forensic Sciences Research (Grabherr S et al.), 2017); Window test for pneumothorax (International Journal of Legal Medicine (Smędra A, Kosmatka P, Berent J), 2026).

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