PATHOLOGY - Body Fluid Analysis

Question 1

Which tube types should you use to collect body cavity effusion samples?

Answer 1

EDTA tube
Plain serum tube

Question 2

What are benefits of using EDTA tubes when sampling body cavity effusions?

Answer 2

EDTA tubes prevent the samples from clotting which can affect the nucleated cell count and helps to preserve the cellular morphology

Question 3

What are benefits of using plain serum tubes when sampling body cavity effusions?

Answer 3

Plain serum tubes can be used for bacterial culture and PCR as EDTA tubes are bacteriostatic

Question 4

What should you assess when evaluating effusion samples?

Answer 4

Colour and turbidity
Protein concentration
Nucleated cell count
Cytological analysis

Question 5

What do you use to assess the protein concentration of effusion samples?

Answer 5

Refractometer (like you would for total serum proteins)

Question 6

What do you use to assess the nucleated cell count of effusion samples?

Answer 6

Automated analyser
Haemocytometer
Estimated from a direct smear

Question 7

What do you use to assess cytology of effusion samples?

Answer 7

Direct smear and microscopy

Question 8

What should you do to allow for cytological analysis of a sample with low cellularity?

Answer 8

Concentrate the sample (can be done by centrifuging the sample and assessing the sediment or using a cytospin)

Question 9

What are the three main classifications of body cavity effusion?

Answer 9

Transudate
Modified transudate
Exudate

Question 10

What causes transudate effusions?

Answer 10

Decreased oncotic pressure
Increased hydrostatic pressure

Question 11

What causes decreased oncotic pressure?

Answer 11

Hypoalbuminaemia

Question 12

What causes hypoalbuminaemia?

Answer 12

Hepatic dysfunction
Protein-losing enteropathy
Protein-losing nephropathy
Third space losses (e.g. loss into abdomen)
Inflammation (negative acute phase protein)

Question 13

What can cause increased hydrostatic pressure?

Answer 13

Congestive heart failure
Portal hypertension

Question 14

What is the gross appearance of transudate?

Answer 14

Colourless to straw coloured

Question 15

What are the features of transudate?

Answer 15

Low protein levels (less than 25g/L)
Low nucleated cell count (less than 1.5 x 10^9 cells/L)

Really low protein can be indicative of hypoalbuminaemia

Question 16

Which cells are typically found in transudate?

Answer 16

Mesothelial cells
Macrophages
Non-degenerate neutrophils

Question 17

How does the composition of transudate differ in horses?

Answer 17

Horse transudate can have nucleated cell counts up to 10 x 10^9 cells/L and have more non-degenerate neutrophils

Question 18

What causes exudate effusions?

Answer 18

Inflammation as it increases vascular permeability which allows intravascular fluid, cells and proteins to move out of the intravascular space

Question 19

What are features of exudate?

Answer 19

High protein levels (above 25g/L)
High nucleated cell counts (above 5 x 10^9 cells/L)

Question 20

How does the composition of exudate differ in horses?

Answer 20

Horse exudate will have nucleated cell counts above 10 x 10^9 cells/L

Question 21

What do you need to determine if you are presented with an exudate effusion sample?

Answer 21

You need to determine if the exudate is septic or not through doing a direct smear to look for the presence of pathogens and degenerate neutrophils (depending on the bacteria the neutrophils may be normal) . You can also culture the fluid if you suspect there is bacteria involved but you cannot see it on the smear

Question 22

What is modified transudate?

Answer 22

Modified transudate is where the protein levels and nucleated cell count are elevated beyond a transudate but are not within the exudate reference range

Question 23

What are the causes of a modified transudate?

Answer 23

Progression of a transudate
Mild inflammation

Question 24

How can a transudate progress to a modified transudate?

Answer 24

When a transudate accumulates in a body cavity this can cause increased pressure on the mesothelium resulting in irritation of the mesothelial cells. The mesothilial cells will proliferate and slough off in response to this irritation (reactive mesothelial cells) as well as draw in macrophages which will increase the nucleated cell count

Question 25

What can reactive mesothelial cells sometimes be mistaken for?

Answer 25

Neoplastic cells

Question 26

What are the classifications of 'special' body cavity effusions?

Answer 26

Chylous effusion Feline infectious peritonitis (FIP) effusion Neoplastic effusion Haemorrhagic effusion Urinary tract rupture Bile peritonitis

Question 27

What is a chylous effusion?

Answer 27

A chylous effusion is caused by the leakage of chyle from the lymphatic system into the body cavities

Question 28

What is the most common site for a chylous effusion?

Answer 28

Chylothorax

Question 29

What are the potential causes of a chylous effusion?

Answer 29

Idiopathic Mediastinal mass Cardiovascular disease Diaphragmatic hernia Lung lobe torsion Trauma

Question 30

What is the gross appearance of a chylous effusion?

Answer 30

Chyle has a milky white to 'strawberry milk' appearance if there is blood present

Question 31

What causes the milky appearance of a chylous effusion?

Answer 31

Chylomicrons are formed in the small intestinal mucosa and transported to the blood stream via the lymphatic system. The chylomicrons give a chylous effusion a milky appearance

Question 32

How does the appearance of a chylous effusion differ in anorexic patients?

Answer 32

In anorexic patients, there will be no chylomicron formation and thus the chylous effusion will not have a milky appearance

Question 33

What are the cytological features of a chylous effusion?

Answer 33

Lymphocytes predominately Neutrophils and macrophages if there has been inflammation

Question 34

Which additional test can you do to confirm a diagnosis of a chylous effusion?

Answer 34

You can compare the serum triglyceride levels to the effusion triglyceride levels. If the effusion triglyceride levels are higher than the serum levels, this indicates a chylous effusion

Question 35

What is the gross appearance of a feline infectious peritonitis (FIP) effusion?

Answer 35

Odourless, straw-coloured to gold fluid

Question 36

What are the features of a feline infectious peritonitis (FIP) effusion?

Answer 36

Hight protein levels *(above 35g/L)* Variable but often low nucleated cell count

Question 37

Which cell type usually predominates a feline infectious peritonitis (FIP) effusion?

Answer 37

Neutrophils

Question 38

Which additional tests can you do to investigate a potential feline infectious peritonitis (FIP) effusion?

Answer 38

Feline coronavirus (FCoV) antibiody titre on the sample Alpha 1-AGP levels *(acute phase protein)* Albumin:globulin ratio PCR for FCoV RNA

Question 39

What are the limitations of a feline coronavirus (FCoV) antibody titre?

Answer 39

A feline coronavirus (FCoV) antibody titre only confirms exposure to FCoV but does not confirm an active infection. Furthermore, it does not differentiate between enteric feline coronavirus and feline infectious peritonitis (FIP)

Question 40

What are the benefits of assessing the albumin:globulin ratio of effusions?

Answer 40

Increased globulins relative to albumin are indicative of inflammation

Question 41

What are the limitations of a PCR for FCoV RNA?

Answer 41

A PCR for FCoV RNA does not differentiate between enteric feline coronavirus and feline infectious peritonitis (FIP)

Question 42

How do you differentiate between a true haemorrhagic effusion and an iatrogenic haemorrhagic effusion?

Answer 42

A true haemorrhagic effusion will have erythrophagocytosis, haematoidin and haemosiderin unlike an iatrogenic haemorrhagic effusion. If you note platelets this is indicative of an iatrogenic haemorrhage during sampling as platelets have a short lifespan

Question 43

What are the characteristics of a uroabdomen?

Answer 43

This type of effusion will vary depending on the urine specific gravity (USG) of the urine that has leaked and the degree of inflammatory response elicited by the urine - as urine is an irritant *(i.e. it may be transudate, modified transudate or exudate)*

Question 44

Which additional tests can be done to confirm a uroabdomen?

Answer 44

You can compare the serum creatinine levels to the effusion creatinine levels. If the effusion creatinine levels are higher than the serum levels, this indicates urine

Question 45

Which additional test can be done to confirm a bile peritonitis?

Answer 45

You can compare the serum bilirubin levels to the effusion bilirubin levels. If the effusion bilirubin levels are higher than the serum levels, this indicates bile

Question 46

When is sampling of cereborspinal fluid (CSF) indicated?

Answer 46

Neurological disease Neck or limb pain Pyrexia of unknown origin

Question 47

Which type of tube should you use to take a cerebrospinal fluid (CSF) sample?

Answer 47

Plain serum tube

Question 48

How should you send cerebrospinal fluid (CSF) samples to an external lab?

Answer 48

If you are posting cerebrospinal fluid (CSF) samples to an external lab, if the volume of sample allows, send two aliquots. Send one in a pain serum tube and one with autologous serum for better cell preservation

Question 49

Why does cerebrospinal fluid (CSF) require rapid analysis?

Answer 49

Cerebrospinal fluid (CSF) requires rapid analysis as the cells will degenerate very quickly

Question 50

What should you use to do a nucleated cell count on cerebrospinal fluid (CSF)?

Answer 50

Haemocytometer as the cell count is often too low for an automated analyser

Question 51

What should you use to do cytology on cerebrospinal fluid (CSF)?

Answer 51

Cytospin to concentrate the sample and stain with Romanowsky stain

Question 52

What are the characteristics of cerebrospinal fluid (CSF)?

Answer 52

Very low protein count Very low nucleated cell count

Question 53

What are the indicators for synovial fluid sampling?

Answer 53

Joint swelling Limping Monoarthropathy Polyarthropathy Pyrexia on unknown origin Generalised pain Generalised weaknesss

Question 54

What is the gross appearance of synovial fluid?

Answer 54

Transparent and viscous fluid

Question 55

Which tests should you prioritise if you can only get a small sample of synovial fluid?

Answer 55

If you only get a small volume of synovial fluid, do a direct smear as this will allow for cytology

Question 56

Which tests should you do if you can get a larger sample of synovial fluid?

Answer 56

EDTA for nucleated cell count and protein levels Plain serum tube for bacterial culture Direct smear