Interpretation in pathology

Question 1

What are pathological lesions?

Answer 1

• are morphological changes in a tissue, caused by disease or trauma
• this may be significant or incidental

Question 2

Other changes can occur in tissues which may be confused with pathological lesions what are examples of these?

Answer 2

• agonal changes (in and around the time of death)
• post mortem changes
• iatrogenic changes (clinical procedures)
• variations in anatomy

Question 3

What is gross pathology?

Answer 3

• 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 (PME)

Question 4

What are the 4 potential outcomes of gross pathology?

Answer 4

• definitive diagnosis based on appearance alone
• determine potential problem which may correlate with clinical signs an support a presumptive diagnosis
• suggest pathogenesis or mechanism of a disease
• changes not distinct enough to establish a diagnosis = further tests required

Question 5

A pathologist needs to determine if the change is significant or incidental - what is a significant change?

Answer 5

• contributed to pathogenesis/ clinical signs/ morbidity/ mortality in the case

Question 6

What is an incidental change?

Answer 6

• unrelated to the case, found as a result of the examination and/or sampling

Question 7

Incidental changes may be related to signalment - what are examples of this?

Answer 7

• species/strain/breed related changes
• age related changes
• sex related changes

Question 8

Incidental changes may be coincidental findings - give an example of this:

Answer 8

• discovering a neoplasia in an animal killed by a traumatic injury

Question 9

How may be go about interpreting the significance of gross changes?

Answer 9

• may need to undertake further examination such as histopathology (microscopic examination)
• need to be interpreted in the context of the case history

Question 10

What are agonal changes?

Answer 10

• changes that occur at or around the time of death
• often due to mechanism of death

Question 11

What are examples of agonal changes from barbital euthanasia?

Answer 11

• splenic congestion
• pulmonary oedema
• barbiturate crystals

Question 12

What are post mortem changes?

Answer 12

• changes to tissues that occur after death

Question 13

Post mortem changes can vary depending on what?

Answer 13

• the condition of the carcass at death
• the environmental condition during the period between death and post mortem (post mortem interval, PMI)

Question 14

What do post mortem changes need to be differentiated from?

Answer 14

• need to be differentiated from pathological lesions

Question 15

What things do pathologists need to know before PME?

Answer 15

• the storage conditions of the body
• environmental conditions, refrigerated, frozen, exhumed

Question 16

What is algor mortis?

Answer 16

• the cooling of the body after death

Question 17

Algor mortis can vary due to what factors?

Answer 17

• species = faster in smaller animals
• site of temperature measurement
• insulation = slower in animals with lots of hair/wool/adipose tissue
• slower in herbivores (continued fermentation generates heat)
• environmental temperature conditions
• state of animal before death (haemorrhage, pyrexia, sepsis, activity before death, wounds)

Question 18

What is rigor mortis?

Answer 18

• contraction of the muscles after death

Question 19

What causes rigor mortis?

Answer 19

• due to the lack of ATP to allow the breakdown of crosslinking in muscle fibres
• subsides with autolysis of the muscle

Question 20

Where is rigor mortis absent?

Answer 20

• in emaciated animals (lack of muscle mass)
• or in very cold conditions (may be confused with freezing)

Question 21

When is rigor mortis more rapid?

Answer 21

• rapid if there is activity before death
  e.g., seizure, struggle

Question 22

In what circumstance may rigor mortis be instantaneous?

Answer 22

• electrocution

Question 23

What is livor mortis?

Answer 23

• the sinking of blood in vessels
• can see body position when dead or if a body has been moved

Question 24

In livor mortis how does blood pool?

Answer 24

• pool sites are dependent due to gravity

Question 25

The blood in livor mortis does what after a period of time?

Answer 25

- eventually sets so the pattern will remain despite moving the body after death

Question 26

What should you check to make sure your not seeing hypostatic congestion (livor mortis)?

Answer 26

- should always check for symmetry when you see a colour change

Question 27

How would you differentiate between hypostasis (livor mortis ) and bruising?

Answer 27

- bruising is outside the vessel - hypostasis is blood sinking in the vessel

Question 28

What are post mortem blood clots like?

Answer 28

- will not be adhered to vessel walls and they form coasts of the vessels in which they are found - pale portion (chicken fat clot) - red portion (red current jelly clot)

Question 29

What are ante mortem thrombi like?

Answer 29

- thrombi in arteries will be attached to the artery wall, are often dry and taper off in the direction of blood flow before death - venous thrombi may be attached to the vessel wall but may resemble post mortem clots

Question 30

What is bloating?

Answer 30

- gaseous distension of the gastrointestinal tract due to the production of gas by microbial activity

Question 31

What problems can bloating cause in a PME?

Answer 31

- can squish the organs and change what we are trying to interpret

Question 32

What is taphonomy?

Answer 32

- the study of the processes that affect the decomposition, dispersal, erosion, burial and re-exposure of organism after, at and even before death

Question 33

What is autolysis?

Answer 33

- breakdown of tissue as a result of enzymes contained within cells = self-digestion

Question 34

What is putrefaction?

Answer 34

- breakdown of tissue by microbial action

Question 35

What are forms of decomposition?

Answer 35

- scavenging - desiccation and mummification = both forms of decomposition

Question 36

What are the classical stages of decomposition?

Answer 36

1. fresh 2. primary bloat 3. activate decay 4. advanced decay 5. skeletonization

Question 37

What is desiccation and mumification?

Answer 37

- loss of water from tissues exposed to air after death

Question 38

What body parts are most susceptible to desiccation and mummification?

Answer 38

- eyes and mucous membranes

Question 39

What organ desiccates more slowly?

Answer 39

- skin

Question 40

What conditions are required for mummification?

Answer 40

- can occur with low humidity and adequate ventilation

Question 41

What is forensic entomology?

Answer 41

- predictable colonisation of a cadaver after death in different environments by different invertebrate life stages and species

Question 42

What is the best way to identify post mortem interval?

Answer 42

- forensic entomology

Question 43

What can forensic entomologists provide?

Answer 43

- advice for sampling - live and preserved samples - can be a data logger (left at the scene to provide data for interpretation)

Question 44

What are the limitation of forensic entomology?

Answer 44

- educator of investigators - entomological evidence collection - absence of invertebrates in some cases or loss during body recovery - lack of environmental/meteorological data for a scene

Question 45

Biochemistry and microbiology is ongoing research what could it be used alongside or replace in the future?

Answer 45

- forensic entomology

Question 46

INFO CARD:

Answer 46

Biochemistry: - large number of parameters to choose from - requires standardisation and validation Microbiology: - exciting prospects for PMI and other forensic applications

Question 47

What are pigments due to post mortem changes?

Answer 47

- haemoglobin imbibition - bile imbibition - pseudomelanosis

Question 48

What is haemoglobin imbibition?

Answer 48

- staining of tissues by haemoglobin pigment due to erythrocyte rupture after death

Question 49

What is bile imbibition?

Answer 49

- staining of tissues by bile pigment leach out from the gall bladder after death

Question 50

What is Pseudomelanosis?

Answer 50

- blue-green/green-black discolouration from hydrogen sulphide created by putrefying bacteria

Question 50

What is normal colour determined by?

Answer 50

- innate colour and number of cells - special pigments - adipose tissue - amount of blood in the vascular bed

Question 51

What is the pigment : tissue ratio like in dark tissues?

Answer 51

= high pigment to tissue ratio

Question 52

What is the pigment : tissue ratio like in light tissues?

Answer 52

= low pigment : tissue ratio

Question 53

Pigments can be split into what?

Answer 53

- endogenous - exogenous

Question 54

Haemorrhage (extravasation of RBCs), congestion, lysis of RBCs, and aging bruises can impart what pigment?

Answer 54

- red-brown, green and yellow pigments to tissues (dependent on stage of process)

Question 55

What is icterus?

Answer 55

- Staining of tissues yellow by bile pigments due to pre-, intra- or post-hepatic causes

Question 56

Some drugs can cause staining - give an example:

Answer 56

- e.g. tetracycline discolouring developing teeth and bones

Question 57

How can fibrosis cause pigment loss?

Answer 57

- Loss of tissue pigment due to replacement with fibrous connective tissue

Question 58

Melanin pigment may be present as part of normal colouration, in discrete areas (melanosis) - where can it be increased or decreased?

Answer 58

- increased or decreased as part of some inflammatory changes, or tumours (melanoma)

Question 59

Fungi, bile, eosinophil infiltrates can cause what discolouration?

Answer 59

- green discolouration to tissue

Question 60

Carotenoids can cause what discolouration?

Answer 60

- Yellow discolouration to plasma and lipid laden cells

Question 61

where can tattoos, carbon and other dusts be found in the body?

Answer 61

- Can be present in tissues and migrate to local lymph nodes