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SMALL ANIMAL > 4.3.4: Anaemia - aetiology and pathogenesis > Flashcards

4.3.4: Anaemia - aetiology and pathogenesis Flashcards

1
Q

How can we detect anaemia on clinical exam?

A
  • Inadequate perfusion/ oxygenation
  • Pale mucous membranes
  • Lethargy, exercise intolerance
  • Compensatory mechanisms e.g. tachypnoea, tachycardia
  • Other signs: poor pulse quality, haemic (flow) heart murmur
  • Signs related to underlying pathology e.g. pain, icterus, melena
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2
Q

Anaemia

A

decreased haematocrit (Hct) (a.k.a. Packed Cell Volume, PCV) or haemoglobin (Hb)

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3
Q

Normal PCV dog

A

35-55%

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4
Q

Normal PCV cat

A

25-45%

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5
Q

Why is it useful to compare PCV to TP?

A
  • TP is useful to combine with PCV to give us an idea of hydration status
  • e.g. if animal with tacky mm and high TP (suggests dehydration) also have PCV on very low end of normal, we might suspect that if properly hydrated, the animal would be anaemic
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6
Q

1

A

Normal

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7
Q

2

A
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8
Q

3

A
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9
Q

4

A
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10
Q

5

A
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11
Q

What are some non-pathological causes that lead to apparent anaemia?

A
  • Splenic relaxation e.g. anaesthetic agents -> sequestration of RBCs in spleen
  • Physiologic anaemia in young animals due to rapid growth rate with haemodilution from plasma volume expansion, dilutional from ingested colostrum, destruction of foetal RBCs and low EPO in first few months of life
  • Overhydration will dilute the RBCs present and falsely lower the PCV
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12
Q

What are the broad causes of anaemia?

A

RBC loss due to trauma or coagulopathy.
RBC destruction in haemolysis - could have immune-mediated/ infectious/ toxic cause
Reduced RBC production by bone marrow - could have genetic/ immune-mediated/ chronic disease/ nutritional (iron-deficiency anaemia) and other causes

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13
Q

Mean corpuscular volume (MCV)

A

average RBC size

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14
Q

Mean corpuscular haemoglobin concentration (MCHC)

A

the amount of haemoglobin in RBCs; will be affected by any changes in cell volume too

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15
Q

Hyperchromic

A

MCV above reference interval (i.e. high Hb)
* Usually a false increase because cells can’t pack in more Hb than usual
* e.g. lipaemia can falsely elevate Hb concentration relative to the PCV, thus falsely increasing the MCHC

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16
Q

Polychromatic

A

lots of colours/ variability of RBC colour

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17
Q

Normochromic

A

MCHC within the reference interval

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18
Q

Hypochromic

A

Lighter in colour/ MCHC below the reference interval

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19
Q

How can you decide if an anaemia is regenerative or not?

A
  • Presence of immature, anucleate RBCs -> reticulocytes
  • Nucleated RBCs (nRBCs) are more common in regenerative anaemia
  • Basophilic stippling = blue dots in cytoplasm of RBCs which correspond to ribosomes not present in mature RBCs -> seen more in regenerative anaemia
  • Howell-Jolly bodies -> seen more in regenerative anaemia
  • Increased numbers of Heinz bodies -> seen more commonly in regenerative anaemia
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20
Q

What are Howell-Jolly bodies and which form of anaemia are they more commonly seen with?

A

Howell-Jolly bodies: remnants of nuclear material from when RBCs change from nucleated to non-nucleated in the maturation process.

Seen more commonly with regenerativ anaemia.

21
Q

1 and 2

A
22
Q

3 and 4

A
23
Q

What are the two likely conditions causing regenerative anaemia?

A
  • Haemorrhage
  • Haemolysis
24
Q

How long does bone marrow take to respond to loss of RBCs and what implications does this have?

A
  • Bone marrow takes 3-5 days to respond to anaemia
  • This means acute conditions may initially appear non-regenerative
  • Also important to remember that chronic haemorrhage or haemolysis that was once regenerative will eventually becoming non-regenerative
25
Q

Describe changes in WBCs that might be seen with different causes of anaemia

A
  • Increased/abnormal WBCs may suggest inflammatory/ neoplastic process that is concurrent with/ causing the anaemia
  • e.g. pronounced neutrophilia -> suspect bacterial infection
  • e.g. abnormal circulating lymphocytes -> suspect neoplasia
  • IMHA commonly accompanied by moderate-severe leucocytosis: typically neutrophilia with a left shift, even in primary/ idiopathic cases
26
Q

What do we call IMHA + IMTP?

A

Evan’s syndrome

27
Q

Why might thrombocytopaenia occur concurrently with anaemia?

A
  • Sometimes platelets are being destroyed too e.g. Evan’s syndrome = IMTP + IMHA
  • Platelets may be being sequestered e.g. in DIC
28
Q

Which cell type is shown here?

A
29
Q

Which cell type is shown here?

A
30
Q

True/false: acute blood loss may not cause anaemia (because whole blood is being lost, so % of RBCs does not immediately change), but when anaemia is seen, it will be regenerative.

A

False
When anaemia is seen, it will be non-regenerative, because in the acute stages (i.e. less than 3-5 days) the bone marrow has not yet had time to respond and regenerate.

We can call this pre-regenerative

31
Q

How could iron-deficiency anaemia occur in relation to blood loss and would this be regenerative or non-regenerative?

A
  • If blood loss is chronic, animal could develop iron deficiency anaemia
  • Iron is needed for haemoglobin so when iron is lost in significant amounts, a microcytic hypochromic (small, light coloured RBC) anaemia is seen
  • Iron-deficiency anaemia is non-regenerative
32
Q

Which is often more severe and acute for the animal: intravascular or extravascular haemolysis?

A

Intravascular

33
Q

Which type of haemolysis is caused by IMHA?

A
  • IMHA can cause both intravascular and extravascular destruction of RBCs via a Type II (antibody-dependent cytotoxicity) mechanism
34
Q

Clinical signs of haemolytic anaemia

A
  • Clinical signs associated with haemoglobin catabolism: haemoglobinaemia, haemoglobinuria, icterus (serum goes icteric before tissues do)
  • Other signs of systemic illness related to underlying disease process e.g. infectious disease, neoplastic mass, toxin exposure, drugs; pyrexia, weight loss, lethargy, inappetance
  • Haematological findings : spherocytes, neutrophilia + left shift, leucocytosis in some dogs, IMTP, presence of RBC parasites, indicators of regeneration e.g. high reticulocytes, HJ bodies
35
Q

Which cells are indicated by the blue arrows and how are they formed?

A

Spherocytes
These are the result of incomplete destruction of RBCs e.g. in haemolytic anaemia

36
Q

Diagnosis of IMHA

A
  • Autoagglutination (pictured in capullary tube)/ slide agglutination test
  • Coombe’s test/ Direct Antibody Test
37
Q

What are some intra-marrow factors that would directly affect bone marrow and what type of anaemia would they produce?

A

Intra-marrow factors -> produce non-regenerative anaemia
Examples
* Infection
* Chronic damage
* Neoplasia
* Lack of raw-materials e.g. iron deficiency

38
Q

What are some extra-marrow factors that would indirectly affect bone marrow and what type of anaemia would they produce?

A

Extra-marrow factors -> produce non-regenerative anaemia
Examples
* Chronic Kidney Disease
* Excessive oestrogen
* Some types of FeLV

39
Q

Which type of anaemia do we usually see in iron-deficiency anaemia?

A

Microcytic hypochromic non-regenerative anaemia

40
Q

Which type of anaemia do we see in anaemia of inflammation (a.k.a. anaemia of chronic disease)?

A

Normocytic normochromic non-regenerative anaemia

41
Q

Absolute iron deficiency

A
  • When there is not enough iron e.g. due to chronic haemorrhage and thus the loss of iron-rich haemoglobin
  • Can be regenerative or non-regenerative
  • Classically is microcytic hypochromic
42
Q

Hepcidin

A

Hormone and acute phase protein that is critically involved in anaemia of inflammation (a.k.a. chronic disease)
* Made in the liver and increased in state of inflammation
* Acts on iron transporters to reduce the ability of cells to move iron out of them
* Effect = functional iron deficiency: where there is reduced dietary absorption of iron and reduced release of stored iron.

43
Q

Aside from its actions related to iron, how else can inflammation contribute to anaemia?

A
  • Via decreased erythrocyte survival times
  • Via suppression of erythropoiesis by inflammatory cytokines
44
Q

If an animal has a moderate-severe anaemia with mild clinical signs, the anaemia is likely to be:
a) acute
b) chronic

A

b) chronic
The animal has had a period of time to acclimatise to low PCV

45
Q

Which feline virus can infected haematopoietic precursors and thus lead to non-regenerative anaemia?

A

FeLV

46
Q

High levels of which hormone can lead to toxic insult to bone marrow and non-regenerative anaemia?

A

Hyperoestrogenism

47
Q

Toxic injury to the bone marrow is likely to result in…

A

Pancytopaenia: significant reduction in almost all blood cells.

48
Q

If you are suspicious of anaemia, what diagnostics might you undertake?

A
  • If trauma - TFAST, rads, abdo US
  • Coagulopathy - clotting parameters (APTT/ PT)
  • IMHA - autoagglutination, Coombe’s test, imaging is suspect neoplasia, specific disease testing e.g. Mycoplasma, Babesia
  • Chronic disease - haematology, biochemistry, urinalysis, UPC, imaging, endocrine screens as appropriate
  • Bone marrow disease - specific testing e.g. FeLV/FIV snap test, bone marrow aspirate

SMALL ANIMAL (90 decks)

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