Name and describe the three things that can cause a change in leukocyte levels?
- Physiological response - causes a mild mature neutrophilia, lymphocytosis +/- monocytosis, secondary to adrenaline release, short lived, usually occurs in young animals
- Stress response - mild to moderate mature neutrophilia, lymphopenia, eosinopenia +/- monocytosis, response it caused by elevated cortico-steroid levels within the animal, neutrophils from the BM storage pool and marginating pool move into the circulating pool
- Inflammation - mild to marked neutrophilia, lymphopenia and monocytosis, presence of left shift or toxic change, magnitude of changes depends on duration, severity of inflammation, nature of inflammation and species of animal
What are the different causes of inflammation?
- Tissue necrosis
- Immune-mediated disease
- Infectious causes
What is left shift?
When there are immature neutrophils coming into the blood circulation
What is regenerative left shift?
Neutrophilia with mainly mature neutrophils and some immature forms seen
What is degenerative left shift?
More immature forms than mature neutrophils present. The neutrophil count may be normal, mildly raised or reduced.
What is a leukaemoid reaction?
A very high neutrophil count with a strong left shift. It can look like leukaemia but leukaemiod reactions are caused by severe inflammatory stimulus.
What is toxic change?
When neutrophils have dohle bodies, increased cytoplasmic basophilia, cytoplasmic vacillation, toxic granulation, cell and nuclear swelling, giant neutrphils - ring forms.
Why does the neutrophil numbers in ruminants drop initially and then rise again after a few days?
This is because they have a very small store of neutrophils so it will take the bone marrow a few days to respond.
What is leukaemia?
The uncontrolled proliferation of one type of WBCs. This starts in the bone marrow and spills out into the blood where it can infiltrate the tissues (commonly the liver and spleen).
How can leukaemia be diagnosed on routine haematology?
By looking at the buffy coat of an animals blood (the buffy coat is the white layer on the of the RBCs composed of WBCs and platelets). In leukaemia patients the buffy coat is much bigger than normal.
What are some of the consequences of leukaemia?
- Mylephthisis - replacement of the bone marrow by neoplastic cells (so the bone marrow is no longer able to produce enough blood cells)
- Extramedullary haematopoeisis (EMH) - the liver and spleen retain the ability to make blood cells so when the bone marrow has been wiped out by cancer cells the liver and spleen will try to compensate
- Slenomegaly / hepatomegaly - enlargement of these organs
- Haemodynamics - If very high WBC, blood is thicker thus impairing blood flow through microvasculature
What happens to patients with acute leukaemia?
- Patients become ill very quickly and head downhill quickly
- Immature blast cells are in the circulation
- Most patients are thrombocytopenic and anaemic, sometimes they show pancytopenia
What are some of the clinical signs of acute leukaemia?
- Lethargy, anorexia and weight loss
- Pyrexia, shifting limb lameness
- Bleeding from nose / mouth, melaena
- Neurological signs
- Splenomegaly / hepatomegaly
- Pale mucus membranes
- Mild generalised lymphadenopathy
What happens to patients with chronic leukaemia?
- Slow onset, progresses slowly
- Can be asymptomatic
- Neoplastic cells are well-differentiated i.e. mature cells are in circulation
- May see mild non-regenerative anaemia but generally other cell lines are unaffected
What are some of the clinical signs of chronic leukaemia?
- May be non - incidental finding on routine screening
- Gradual weight loss
- Possible mild splenomegaly / hepatomegaly