Interpretation in pathology Flashcards
What are pathological lesions?
- are morphological changes in a tissue, caused by disease or trauma
- this may be significant or incidental
Other changes can occur in tissues which may be confused with pathological lesions what are examples of these?
- agonal changes (in and around the time of death)
- post mortem changes
- iatrogenic changes (clinical procedures)
- variations in anatomy
What is gross pathology?
- 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)
What are the 4 potential outcomes of gross pathology?
- 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
A pathologist needs to determine if the change is significant or incidental - what is a significant change?
- contributed to pathogenesis/ clinical signs/ morbidity/ mortality in the case
What is an incidental change?
- unrelated to the case, found as a result of the examination and/or sampling
Incidental changes may be related to signalment - what are examples of this?
- species/strain/breed related changes
- age related changes
- sex related changes
Incidental changes may be coincidental findings - give an example of this:
- discovering a neoplasia in an animal killed by a traumatic injury
How may be go about interpreting the significance of gross changes?
- may need to undertake further examination such as histopathology (microscopic examination)
- need to be interpreted in the context of the case history
What are agonal changes?
- changes that occur at or around the time of death
- often due to mechanism of death
What are examples of agonal changes from barbital euthanasia?
- splenic congestion
- pulmonary oedema
- barbiturate crystals
What are post mortem changes?
- changes to tissues that occur after death
Post mortem changes can vary depending on what?
- the condition of the carcass at death
- the environmental condition during the period between death and post mortem (post mortem interval, PMI)
What do post mortem changes need to be differentiated from?
- need to be differentiated from pathological lesions
What things do pathologists need to know before PME?
- the storage conditions of the body
- environmental conditions, refrigerated, frozen, exhumed
What is algor mortis?
- the cooling of the body after death
Algor mortis can vary due to what factors?
- 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)
What is rigor mortis?
- contraction of the muscles after death
What causes rigor mortis?
- due to the lack of ATP to allow the breakdown of crosslinking in muscle fibres
- subsides with autolysis of the muscle
Where is rigor mortis absent?
- in emaciated animals (lack of muscle mass)
- or in very cold conditions (may be confused with freezing)
When is rigor mortis more rapid?
- rapid if there is activity before death
e.g., seizure, struggle
In what circumstance may rigor mortis be instantaneous?
- electrocution
What is livor mortis?
- the sinking of blood in vessels
- can see body position when dead or if a body has been moved
In livor mortis how does blood pool?
- pool sites are dependent due to gravity
The blood in livor mortis does what after a period of time?
- eventually sets so the pattern will remain despite moving the body after death
What should you check to make sure your not seeing hypostatic congestion (livor mortis)?
- should always check for symmetry when you see a colour change
How would you differentiate between hypostasis (livor mortis ) and bruising?
- bruising is outside the vessel
- hypostasis is blood sinking in the vessel
What are post mortem blood clots like?
- 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)
What are ante mortem thrombi like?
- 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
What is bloating?
- gaseous distension of the gastrointestinal tract due to the production of gas by microbial activity
What problems can bloating cause in a PME?
- can squish the organs and change what we are trying to interpret
What is taphonomy?
- the study of the processes that affect the decomposition, dispersal, erosion, burial and re-exposure of organism after, at and even before death
What is autolysis?
- breakdown of tissue as a result of enzymes contained within cells = self-digestion
What is putrefaction?
- breakdown of tissue by microbial action
INFO CARD:
- scavenging
- desiccation and mummification
= both forms of decomposition
What are the classical stages of decomposition?
- fresh
- primary bloat
- activate decay
- advanced decay
- skeletonization
What is desiccation and mumification?
- loss of water from tissues exposed to air after death
What body parts are most susceptible to desiccation and mummification?
- eyes and mucous membranes
What organ desiccates more slowly?
- skin
What conditions are required for mummification?
- can occur with low humidity and adequate ventilation
What is forensic entomology?
- predictable colonisation of a cadaver after death in different environments by different invertebrate life stages and species
What is the best way to identify post mortem interval?
- forensic entomology
What can forensic entomologists provide?
- advice for sampling - live and preserved samples
- can be a data logger (left at the scene to provide data for interpretation)
What are the limitation of forensic entomology?
- 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
Biochemistry and microbiology is ongoing research what could it be used alongside or replace in the future?
- forensic entomology
INFO CARD:
Biochemistry:
- large number of parameters to choose from
- requires standardisation and validation
Microbiology:
- exciting prospects for PMI and other forensic applications
What are pigments due to post mortem changes?
- haemoglobin imbibition
- bile imbibition
- pseudomelanosis
What is haemoglobin imbibition?
- staining of tissues by haemoglobin pigment due to erythrocyte rupture after death
What is bile imbibition?
- staining of tissues by bile pigment leach out from the gall bladder after death
What is Pseudomelanosis?
- blue-green/green-black discolouration from hydrogen sulphide created by putrefying bacteria
What is normal colour determined by?
- innate colour and number of cells
- special pigments
- adipose tissue
- amount of blood in the vascular bed
What is the pigment : tissue ratio like in dark tissues?
= high pigment to tissue ratio
What is the pigment : tissue ratio like in light tissues?
= low pigment : tissue ratio
Pigments can be split into what?
- endogenous
- exogenous
Haemorrhage (extravasation of RBCs), congestion, lysis of RBCs, and aging bruises can impart what pigment?
- red-brown, green and yellow pigments to tissues (dependent on stage of process)
What is icterus?
- Staining of tissues yellow by bile pigments due to pre-, intra- or post-hepatic causes
Some drugs can cause staining - give an example:
- e.g. tetracycline discolouring developing teeth and bones
How can fibrosis cause pigment loss?
- Loss of tissue pigment due to replacement with fibrous connective tissue
Melanin pigment may be present as part of normal colouration, in discrete areas (melanosis) - where can it be increased or decreased?
- increased or decreased as part of some inflammatory changes, or tumours (melanoma)
Fungi, bile, eosinophil infiltrates can cause what discolouration?
- green discolouration to tissue
Carotenoids can cause what discolouration?
- Yellow discolouration to plasma and lipid laden cells
where can tattoos, carbon and other dusts be found in the body?
- Can be present in tissues and migrate to local lymph nodes
