Anaemia Flashcards
Define the term ‘anaemia’
A decreased haematocrit, packed cell volume or haemoglobin
What is a haematocrit?
Calculated value from the mean cell volume, red blood cell count and haemoglobin concentration (provided by automatic analysers)
Can be affected by machine errors
HCT = (MCV x RBC count) + 10
Define the term ‘PCV’
Directly measured value measured as a percentage of packed red blood cells in blood volume
Affected by how RBCs pack together
Normally measured by a person due to machine errors
What is a normal dog PCV?
35-55%
About half the haematocrit should be red
Give 4 clinical signs which can be caused by anaemia
Pale mucous membranes
Lethargy and exercise intolerance
Tachypnoea
Tachycardia
Poor pulse quality
Haemic/Flow murmur
Splenomegaly
Lymphadenopathy
Pain
Pica
Icterus
Melaena
What are the 3 causes of apparent non-pathological anaemia?
Young animals
Anaesthesia
Overhydration
How does anaemia cause a haemic or flow murmur?
Diluted blood is less viscous, so makes a whooshing sound on auscultation
True or false?
The severity of anaemia is linked to their clinical condition
False
Can be helpful during diagnosis as severe anaemia is rarely caused due to chronic disease, but then as chronic disease progresses the severity of anaemia does too
What are the 4 ways to categorise anaemia?
- Severity - not 100% reliable
- RBC indices
- Regeneration
- Other haematology clues
Why do animals with chronic anaemia often look clinically healthier than animals with acute anaemia?
Chronic animals look a lot better on low PCVs than acute animals as they’ve had time to compensate for it
Chronic disease takes up a lot of effort from the body, so the bone marrow struggles to keep up, but not that severe
How are red blood cells categorised?
Size
Colour
Shape
Cellular contents
What is the Mean Corpuscular Volume (MCV)?
Average volume of the red blood cells - will change if large or small red blood cells are present
What is the Mean Corpuscular Haemoglobin Concentration (MCHC)?
Amount of haemoglobin in red blood cells
Dependent on the absolute amount of haemoglobin and cell volume
What do the terms normocytic and microcytic mean?
Normocytic = MCV within the reference interval
Microcytic = MCV below reference interval = small cells
Hyperchromic blood contains high levels of haemoglobin, leading to darker coloured blood. What can cause it to falsely elevate?
Lipaemia
Normally a false increase, so tend to ignore if it occurs
What is the term used to describe red blood cells which are variable in colouration?
Polychromatic
Are hypochromic red blood cells darker or lighter than normochromic red blood cells?
Lighter with less colour
MCHC below the reference interval
Red blood cells start as rubriblasts in the bone marrow. Name the stages that red blood cells go through before they become mature.
- Rubriblast
- Prorubricyte
- Rubricyte
- Metarubricyte
- Reticulocyte
- Mature red blood cell (in circulation)
Stages 1-5 occur in the bone marrow, before reticulocytes enter the blood stream
How many hours does a reticulocyte take to mature in the blood stream?
24-48
What is the name given to any normal, healthy cell that is the immediate precursor of normal, healthy, mature (anucleate) RBCs?
Normoblast - nucleated red blood cell
How does the size of red blood cell precursors and haemoglobin concentration change as they mature?
Maturity results in the cells getting smaller and accumulating more haemoglobin
What does the presence of excess numbers of reticulocytes in the bloodstream mean?
Bone marrow is actively trying to correct the reduced red blood cell number
What term describes red blood cells with a variety of sizes?
Anisocytosis
Name 4 non-specific markers which are RBC indicators more common in regenerative anaemia
Nucleated red blood cells
Basophilic stippling
Howell-Jolly bodies
Heinz bodies
What is the difference between Howell-Jolly bodies and Heinz bodies?
Howell-Jolly bodies: small fragments of non-functional nuclei inside red blood cells; normal in cats and horses or associated with increased red blood cell turnover or splenic disease (fragments removed by the spleen); found within the red blood cell
Heinz bodies: denatured haemoglobin inside red blood cells; result of oxidative damage to erythrocytes; seen right on the edge of red blood cells, and often just outside
Does MCV increase, decrease or stay the same in regenerative anaemia?
MCV increases as reticulocytes are larger than erythrocytes
What is the main cause of high reticulocyte levels in the blood?
Haemorrhage
Haemolysis
What are the 3 main causes of non-regenerative anaemia?
Decreased bone marrow production of erythrocytes
Pre-regenerative anaemia - bone marrow takes 3-5 days to respond to anaemia so acute conditions may initially appear non-regenerative
Chronic haemorrhage or haemolysis - even if it starts regenerative it eventually becomes non-regenerative as bone marrow gives up (run out of iron)
You see a lot of banded neutrophils on a blood smear. What are they?
Younger neutrophils - get more banded as they mature
What is the term given for high numbers of white blood cells?
Leukocytosis
You are looking at a blood smear of a dog with anaemia. There are large numbers of spherocytes. What is a likely cause of this?
Immune-mediated haemolysis
Which cells might you see on a blood smear after a dog or cat has had an intravascular red blood cell injury?
Schistocytes (fragmented red blood cells)
Keratocytes (red blood cells with horns)
What red blood cells would you see after onion toxicity in a dog?
Heinz bodies
Due to heinz body haemolysis or oxidant injury
You have a cat with iron deficiency. What type of cells would you expect to see on a blood smear?
Dacryocytes - teardrop shape red blood cells
Seen in iron deficiency and myelofibrosis (blood cancer of the bone marrow)
When might you see echinocytes (wavy/bubbly/spiky red blood cells) on cytology?
In animals with renal azotaemia or having chemotherapy
What do acanthocytes look like, and when might you see them on a blood smear?
Look like spikier echinocytes
Caused by splenic neoplasia and liver disease
If erythropoiesis is suppressed, do you see regenerative or non-regenerative anaemia?
Non-regenerative
Due to intra-marrow or extra-marrow issues
What are the 3 broad causes of anaemia?
Red blood cell loss - haemorrhage due to trauma or coagulopathy
Red blood cell destruction - e.g. haemolysis
Reduced red blood cell production - by the bone marrrow
Give 2 causes of anaemia due to internal red blood cell loss
GIT disease
Parasites
Pulmonary haemorrhage
Abdominal cavity haemorrhage
Other than trauma, what can cause anaemia due to red blood cell loss?
Coagulopathy
Define the term ‘epistaxis’
Nosebleed
Can cause anaemia through external red blood cell loss (like wounds)