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Negative Autopsy
By Aisha Ghias (KEMC), Mamoona Ghias (PMC)

Definition 
“It is the process including all the physical and chemical efforts which fail to reveal the cause of death”
*About 2-8% of the Autopsies go unrewarded, i.e. Negative.

Limitations
Indicator of the death cannot be found in following cases,

Putrefaction
It is a natural limitation , soft tissue findings are obscured, fragmented bodies and mutilated are also a limitation.

Over freezing
It is a limitation for detecting the indicator by histopathological exam.

Types of Negative Autopsy
(1) True negative autopsy
(2) Pseudo negative autopsy

True Negative Autopsy
(1) Indicator cannot be found, when fatal period is very short,e.g.
* Vagal inhibition of heart.
* Acute neurogenic myocardial failure
* Coronary spasm
* Laryngeal spasm as in dry drowning

(2) No anatomical due to concussion of brain.
(3) Findings are so minor that can not be taken as cause of death e.g. When a person scuffles with a  person having cardiopulmonary deficit, it results in functional ischemia of heart.
(4) Indicator cannot be detected by the present method of investigation,
* Death from early myocardial infarction
* Conductive system defect
* Lesions of parathyroid gland
* Lesions of adrenal gland 

Pseudo Negative Autopsy
It results due to lapses in
* History of case
* External exam.
* Internal exam.
* Histological exam.
* Toxicological exam.
* Lapses in medical person

(1) Lapses in History Of the Case
Commencing autopsy without sufficient history may result in loosing the findings,e.g. death due to pneumothorax,air embolism or vagal inhibition.

(2) Lapses in External Examination
May result in loosing the following lesions, needle mark, snake bite mark, injuries in fontanellae, inside the oral or nasal cavity, nape of neck, umbilicus, rectum and genital organs. 

(3) Lapses in Internal Examination
Air embolism,when death is due to criminal abortion, intravenous therapy, death during delivery, to prevent this, the right ventricle should be opened under water to see the air bubbles.
Death due to pneumothorax, to prevent this lung cavity should be opened under water to see air bubbles.

(4) Lapses in Histological Examination
If proper specimen is not sent or proper part of the specimen is not sent,or if the proper specimen has been sent examiner has not examined the proper section suspected to hav details, or if the specimen is taken from the putrified body,or it is not preserved properly.

(5) Lapses in Toxicological Examination
We send the specimen to the Chemical examiner but
* Specimen is not proper.
* Specimen is not in adequate quantity.
* Specimen is not preserved properly.
* Specimen is not collected in a proper way then it can lead to negative  result. There are certain poisons which are very difficult to detect,
* Volatile poisons
* Vegetable poisons
* Synthetic poisons

(6) Lapses in the Medical Person
The person conducting the autopsy is not having proper knowledge of the subject or he has no practice , he will fail to get result.

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