A complete blood count, also known as haematology, examines the blood
cells in the body.
There are two types of blood cell, red blood cells (RBCs) and white
blood cells (WBCs).
White blood cells help to determine whether a cat has an
infection or inflammation.
Red blood cells help to determine whether a cat is anaemic.
White Blood Cells (WBC)
or Leukocytes: Infection or
White blood cells, sometimes called leukocytes, are the body's defence
system. If inflammation or infection are present anywhere in the body,
or if cancer tries to strike, white blood cells will accumulate near the
source of the assault to fight the invaders, and
therefore the total number of white blood cells will increase.
As part of this process, white blood cells also remove damaged cells and
There are five main types of white blood cells, divided into two groups:
So called because they absorb the stain when they are viewed under a
Because there are so many different types of white blood cell, in order to work out where the problem lies, it is necessary to
differentiate between how many of each type there are. This is called the
differential count, and it usually shows two sets of numbers:
the actual amount of each type of WBC (abbreviated as absolute or ABS);
the percentage of each type.
Normally the absolute count is what is assessed.
explains more about the differential count in older cats.
Some people think that elevated white blood cells always mean an infection
is present, but this is not necessarily the case. It is true that white
blood cells are often increased when fighting an infection, but they may
be elevated for some other reason, such as inflammation. In some cases,
inflammation may be visible i.e. pus, which consists largely of white
There can be inflammation without infection but not vice versa.
There are other possible causes of increased white blood cells, such as the use of
corticosteroids. WBCs are often
very high in cases of
injury (because of the toxins build up and associated inflammation).
Cats with very high WBC levels may also have increased potassium levels.
(2015) explains why elevated white blood
cells do not always mean an infection is present.
White Blood Cells: Decreased
Occasionally, and rather confusingly, cats with inflammation or an
infection may have a decreased number of white blood cells. This is often
the case with a viral (rather than bacterial) infection. It may also be
seen if the cat has been suffering from a chronic or severe infection, to
such an extent that the white blood cells are depleted.
Mature neutrophils are called segmented cells or segs.
Immature neutrophils are called bands.
If severe inflammation or infection are present, more bands are released into the
blood than would normally be the case to help fight it, so the percentage
of bands increases compared to segs. This is sometimes called "a shift to
the left." The higher the number of bands, the more severe the
infection or inflammation.
If total neutrophil levels are high with a left shift, so overall there
are still more segs than bands, this is called a
regenerative left shift. If neutrophil levels are normal or low with a
left shift, and overall there are more bands than segs, this is called a degenerative left shift.
Degenerative left shift as a prognostic tool in cats
(2014) Burton AG, Harris LA, Owens SD & Jandrey KE Journal of
Veterinary Internal Medicine28(3) pp912-7 found that cats
admitted to a veterinary teaching hospital over a fifteen year period who
had a degenerative left shift were 1.57 times more likely to die or be put
to sleep. Cats with leukaemia were most at risk. However, the study does
state "each situation needs to be evaluated individually, as some patients
with DLS can and will recover."
High neutrophil levels (neutrophilia) often indicate that the body is fighting a bacterial
Other possible causes include inflammation or
often low (neutropaenia) in cases of viral infection.
They may also
be low in cases of severe inflammation or bacterial infection where the
body has struggled to keep up with the demand for them.
CKD cats with
uraemia (which tends to apply to most CKD cats)
may have low neutrophil levels.
occasionally have idiopathic neutropaenia, i.e. no obvious cause can be
A lack of
has been known to cause neutropaenia in some breeds of dog.
People can be worried when they see this expression, but don't panic, it
does not mean your cat is being poisoned in some way. Basically it means
that a relatively severe inflammatory process or infection is present that
is driving the bone marrow to work very hard to produce white blood cells
to fight the problem.
The Merck Veterinary Manual states "The
term is misleading in that it implies neutrophil injury. The cells are not
injured and have normal function. Toxic change is best defined as a set of
morphologic changes observed on the blood smear that occur as a result of
accelerated marrow production of neutrophils. The accelerated production
is in response to relatively severe inflammatory states that maximally
stimulate the bone marrow."
Toxic neutrophils often (but not always) are accompanied by a shift to the
left (see Segs and Bands).
leukogram means that the cat has a high neutrophil count with an increase in
segs rather than bands together with a low lymphocyte count (see
"stress" confuses people. Contrary to what you might expect, it does not
mean the cat is stressed by the vet visit, but refers more to chronic
physiological stress. It occurs when a cat has a chronic illness (such as
CKD), so the body is releasing more steroids.
It may also be seen when a cat is being medicated with
Basophils are not seen often in cats, so it is actually normal for the
value to be zero.
As the name suggests, lymphocytes are produced by the lymph glands, and
also by the
spleen. They consist of B cells and T cells:
B cells work by producing antibodies which neutralise the threat
T cells work with other cells to do the same thing.
you may see reference to atypical lymphocytes. This means your cat's
immune system is reacting to something. This might simply be recent
vaccinations or it might be something more serious such as cancer. Your
vet will probably ask a clinical pathologist to review your cat's results
to look for clues as to the possible cause.
Stopping long term
corticosteroids may lead to a temporary increase in lymphocytes.
Lymphocytes are often low in cases of viral infection or when using
steroids. They may also be low in cases of chronic bacterial infections.
CKD cats with
tends to apply to most CKD cats) often have low lymphocytes.
which occurs when a cat has a chronic illness, means the cat may
have a low lymphocyte count with a
high neutrophil count.
Monocytes can be produced in either the bone marrow or the spleen. They
are capable of leaving the blood stream to enter surrounding tissues in
order to reach hostile bacteria. They also remove damaged body cells, so
are often present when there is tissue necrosis (dying tissue).
Their numbers do not usually vary much unless leukaemia (cancer of the
blood) is present.
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
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appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
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