Investigation of episodes of collapse
These conditions are complex to investigate in dogs as there are
very many potential causes and the length of time needed and the
associated costs involved can be, understandably, substantial. It
is not uncommon for investigation of collapse to require several
periods of hospital-based investigation, often by specialists in
more than one discipline since causes may be as diverse as airway
problems, cardiac problems, neurological, orthopaedic, metabolic or
muscular. Within each of these categories, very many potential
causative diseases can exist, all of which can cause intolerance of
exercise.
It is therefore very important, before investigation is
performed, that we are certain that collapse is truly occurring -
collapse is involuntary i.e. if a dog is choosing to lie down, for
instance because of tiredness or heat exhaustion, or because of
feeling faint after pulling hard on the lead this is not collapse.
It is equally important to understand that intermittent collapse
can be frustrating to investigate and may take a long time. Many
common causes of collapse, such as fainting, may be completely
benign and require no treatment.
Some of the potential causes are extremely complex to
investigate and may require procedures which involve tissue biopsy
or which may need to be sent to specialist laboratories around the
world.
HOW DO WE INVESTIGATE COLLAPSE?
The first step with investigation is to ask you a large number
of questions about the collapse. It is also very helpful if you can
provide / show video footage of the events occurring as sometimes
this may show important information which to the untrained eye may
not be obvious.
It is helpful for us to know:
- What your pet is doing just before he or she collapses
- What he or she does during the collapse
- What he or she does after the collapse
After asking you lots of questions we perform a thorough
clinical examination. In some cases, the combination of the history
that you give and the physical examination findings will give us
diagnostic 'clues' as to which direction in which to look
first.
If these findings make one particular cause of collapse more
likely than others than this allows a far better chance of
determining the cause. A problem arises where signs are vague and
do not allow us to 'home in' on a particular group of
possibilities. In these circumstances unfortunately investigation
needs to be very broad-based and we would start by evaluating for
the most common causes of collapse.
WHAT TESTS MAY BE PERFORMED?
It is very difficult to make generalisations as each case is
different However, in general investigation may involve some of the
following tests and procedures:
Blood tests
There is no single test that will evaluate for all causes of
collapse and, unlike media portrayals of medical diagnosis,
'screens' for all causes of collapse do not exist. Tests are picked
on an individual basis according to likelihood. Your vet may have
performed some blood tests, which will have helped rule-out certain
problems. However, they will not have the facilities to measure
some blood components and further blood tests are likely to be
needed. It is quite common for blood samples to need to be sent to
more than one laboratory as many will specialise in particular
areas. Some of these may be outside the UK and some test results
can take some time (even several weeks if they are tests that are
not performed on a daily basis / are batched together to make them
financially practical to perform). We know it can be a trial of
patience waiting for such tests but it is better to wait for
accurate results than to choose a more rapid but less helpful
alternative.
Diagnostic imaging
There are many different types of diagnostic imaging such as
radiography (x-rays), ultrasound examination, fluoroscopy (video
x-ray), computed tomography (CT) and magnetic resonance imaging
(MRI). All of these are available at Dick White Referrals although
CT is performed off-site at a neighbouring equine practice. All of
these tests have advantages and disadvantages and all are helpful
in looking at some tissues but not helpful in looking at others.
Sometimes a combination of imaging may be needed. Although
technologies such as CT and MRI give beautiful tissue detail in
some areas, in others they are not so good and there may be cheaper
and more effective ways of evaluation. A common misconception is
that these provide some sort of 'whole body screen' (indeed some
companies in human medicine market such screens to worried people)
whereas in order to be useful they need to be used with very
specific questions in mind. Part of a medical specialist's skill is
in determining which of these may be most appropriate and in many
instances it will be our advice that such tests may not be
diagnostically helpful.
Diagnostic imaging tests help define abnormalities in the size,
shape, position and structure of tissues and the relationship
between different tissues. Abnormalities which are detected may be
caused by a variety of different problems and it is seldom that
only one is likely.
Imaging tests are particularly useful in evaluating whether
there is cardiac disease (an echocardiogram test), alteration in
blood vessel anatomy, abnormalities of the major organs, and (in
the case of MRI), to evaluate neurological tissue (brain and spinal
cord). MRI is considerably more expensive and time consuming to
perform than other tests and always requires general
anaesthesia.
Analysis for heart rhythm disturbances ('arrhythmias')
Sometimes collapse may be caused by intermittent disturbances in a
pet's heart rhythm. These may occur frequently enough to be
detected on an electrocardiogram (ECG) but very often are so
intermittent that the chances of detecting them whilst the patient
is in the hospital is low. We can increase the chances of detecting
them by performing a 24-hour 'Holter' monitor test, where your dog
wears a unit about the size of a personal music player, that
records the heart rhythm over 24 hours. The unit is then analysed
(this is a long and laborious process that is performed by
clinicians in and amongst seeing other cases, or may be sent away,
and may take a few days) and the results interpreted. Sometimes
rhythm disturbances may occur so infrequently that even this does
not detect problems and in this situation we can sometimes obtain a
unit which is surgically placed in a pocket under the skin and
which measures heart rhythm for a longer time. We are reliant on
altruistic human hospitals for loan of this equipment which limits
its practical use as they can be very difficult to come by.
Other tests
Sometimes tests looking for rare metabolic abnormalities,
inherited disorders and very rare muscular disorders may be needed.
Some of these occur so rarely in animals that laboratories
assessing for these may either only do so very infrequently (when
they have enough samples from different animals to make diagnostic
testing cost-effective) or may be run by colleagues performing
research as a favour in their spare time rather than as a
commercial and rapid service. Please be patient in these
circumstances - it may take many weeks for results to return.
Some rarer neuromuscular diseases and some rare metabolic
defects may only be diagnosed by looking at tissue samples
(biopsies) taken from the muscles or organs like the liver. Again,
tests needed to identify these are infrequently performed in
veterinary species due to how rarely they occur.
WHAT IF NO DIAGNOSIS IS MADE?
Unfortunately sometimes, even despite extensive investigation no
diagnosis is determined. This may mean that there is no
pathological cause for the collapse or, more commonly that the
problem causing it is something that occurs only very
intermittently (and is not occurring at the time of
investigation).
In these circumstances it may be our advice that further
investigation is only performed if clinical signs become worse, if
collapsing occurs more frequently or if initial results were
inconclusive, but are also by the same token not 'quite normal' we
may advise these are repeated at a later stage.
If no problem is found it should be borne in mind that
- just as in people, collapsing may occur occasionally in some
individuals due to common faint - this will not be detectable on
any diagnostic tests
- investigation will have ruled out the most common
life-threatening causes of collapse
If you have worries or concerns or feel that your pet's
condition has changed, please contact us to discuss these concerns.
Episodic collapse, particularly if it is very infrequent, can be a
frustrating problem with which to be faced and we appreciate
this.
If you have access to technology such as mobile phones with
video editing, it can be helpful for us to see episodes occurring
and sometimes our advice will be that such further information may
be invaluable.
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