(W1) Post Mortem Examination Flashcards
What is gross pathology and what are its 4 potential outcomes?
The recognition and description of macroscopic/morphological changes to tissues and organs in the live or dead animal at biopsy, surgical removal or post mortem examination
4 Outcomes:
- definitive diagnosis based on appearance alone
- determine potential problem(s) which may correlate with clinical signs and support a presumptive diagnosis
- suggest pathogenesis or mechanism of disease
- changes not distinct enough to establish a diagnosis - further tests required
What are the 9 reasons why we do post mortem examination (SSHROFDTZ)
Surveillance:
- monitor epidemic disease
- detect exotic/notifiable diseases
- public health
- monitoring effects of husbandry/management changes
Sudden death (SD):
- definition; death without any knowledge of disease, injury or intoxication or death within minutes/hours of onset clinical signs
- post mortem provides diagnosis for death when there isn’t one
- apparent SD i.e. when clinical signs not noticed by owner (e.g. prey animals masking suffering)
Herd, Group or Population Health:
- rapid diagnosis of disease in groups/herds and implement treatment/managements changes to prevent further loos within group
Research:
- toxicological pathology (pharmaceutical toxicity trials (slides of samples given new compound and looked at to assess toxicity of that compound)
- Tissues for further study: clinical, pathology, basic science research, and retrospective studies
Obtaining samples:
- histopathology
- microbiology (bacteriology, virology, mycology
- parasitology
- trace element analysis
- toxicology
Forensic:
- PM in cases that involve animals (cause of death, disease/health status, degree of suffering, obtaining trace evidence, etc)
- Insurance
- malpractice inquests
Confirm or refute a clinical diagnosis:
- to also check whether there was concurrent disease or not
Failure of treatment:
- find out why the treatment failed
- clinical audit
Zoological collection:
- zoo animals have PM examinations routinely
What are the 7 prerequisites for PM examination?
- permission to perform PME
- reason for PME
- signalment (species, breed, sex, age, etc)
- clinical history
- time of death
- mode of death (found death/euthanasia - lethal injection using barbiturates, gunshot, humane killer, etc)
- cadaver storage (room temp, refrigerated, frozen)
Why does the mode of death, especially when lethal injection (barbiturates) is used, important to be noted?
Because the use of barbiturates causes the spleen to become enlarged and also the lungs to be filled with fluid (oedema). This may be mistaken as pathology rather than an agonal change
When examining the subcutaneous tissue in PME, what colours can be present and what do they indicate?
Yellow - icterus (bilirubin)
Pallor - loss of blood (anaemia)
Red-Purple - congestion, sepsis, bruising
Green - bile imbibition (bile leaking through bile ducts and staining the subcutis) and pseudomelanosis (bacteria produce sulphur-containing compounds that are green)
Gelatinous - oedema, serous atrophy of fat
What is an agonal change (give 2 examples)?
changes that occur at or around the time of death (often due to the mechanism of death)
1) Barbiturate euthanasia:
- splenic congestion
- pulmonary oedema
- barbiturate crystals
2) Agonal emphysema (when the alveoli rupture - causes shortness of breath), with congestion and oedema (may see rib imprints?)
What are the 9 post mortem changes (excluding the agonal changes)?
- algor mortis
- rigor mortis
- livor mortis
- bloating
- decomposition (autolysis and putrefaction)
- desiccation
- insect colonisation
- clotting (thrombi are ante mortem!!)
- Haemoglobin/bile imbibition and pseudomelanosis
What is algor mortis and how does it differ between smaller vs larger animals and herbivores? How does this relate to the rate of decomposition?
the cooling of the body after death (it depends on the environmental temperature and conditions)
Faster in:
- small animals
Slower in:
- animals with a lot of fur/wool
- animals with a lot of adipose tissue
- herbivores (continued fermentation generates heat)
In animals where it takes longer for the body to cool down, decomposition occurs at a faster rate as the body remains warmer for longer.
What is rigor mortis, why does it occur and what conditions affect whether it occurs or not?
the contraction of the muscles after death
It occurs due to the lack of ATP that is needed to breakdown the crosslinking in muscle fibres
Conditions:
- absent in emaciated animals (lack of muscle mass) or in very cold conditions (may be mistaken for the freezing of the body)
- rapid if there’s activity before death e.g. seizure, struggle, fighting, etc
Rigor mortis might be instantaneous e.g. in electrocution, and the onset/disappearance of if it highly variable
What is bloating and what may you see in post mortem that indicates it?
the gaseous distention of the GI tract caused by the production of gas by bacteria
E.g. if a cow has bloat, the blood will be squeezed out of the area that’s bloated. At the edge of the tissue/at the border, it will be congested. In oesophagus, you will see bloat line (this indicates that the bloat occurred when the animal was alive)
What are the two processes involved in decomposition?
1) Autolysis - breakdown of tissue as a result of enzymes contained within cells = self-digestion
gall bladder is fastest to autolyse as bile is caustic. Also, pancreas (due to enzymes), brain (due to fat) and intestines (due to bacteria)
2) Putrefaction - breakdown of tissue by bacteria
Together they make up decomposition!!
What is desiccation, what tissues are most susceptible and what conditions can it occur?
the loss of water from tissues exposed to air after death
- eyes and mucous membranes most susceptible
- skin desiccates more slowly
- exposed tissue (e.g. from trauma or scavenging)
Conditions:
- can occur with low humidity and adequate ventilation
What is insect colonisation?
colonisation of a cadaver after death in different environments by different invertebrate life stages and species
forms basis of forensic entomology
What is livor mortis (aka hypostatic congestion), what would you see and how do you differentiate it with bruising?
the pooling of blood in dependent sites due to gravity
- the blood eventually sets so would see patter remain despite moving the body after death
- variable time to appear and set
- check for symmetry when you see colour change (to ensure that you’re not just seeing hypostatic congestion
Hypostasis vs Bruising:
- microscopically, you would see blood cells outside the vessels in bruising but would see blood cells crammed in vessels in hypostasis
What is clotting and how is it different to thrombi?
Clotting:
- POST mortem blood clots not adhered to vessel wall and form casts of the vessels that they are found in
- pale portion = chicken fat clot
- red portion = red current jelly clot
Thrombi:
- ANTE mortem thrombi are attached to artery wall
- they are dry and taper off in direction of blood flow before death
- venous thrombi may be attached to vessel wall but resemble post mortem clots
