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Your veterinarian has many different
types of tests that are at his/her disposal in order to make a diagnosis.
Most tests, however, are indirect measures of the bodys response
to disease. One of the most direct and therefore useful tests that
can be performed is a biopsy. A qualified pathologist then examines
the tissue that is taken from the area or organ in question under
a microscope. This is probably the best means of confirming a tentative
diagnosis.
There are several techniques for obtaining
a biopsy. A needle biopsy is a method whereby a small core sample
is taken for analysis. This method has the advantage of being relatively
noninvasive, quick and easy to perform. Needle biopsies are most
often applied when the tissue is easy to reach such as with a surface
growth. The down side of this method is the small sample size and
that it is a blind procedure which may not be representative
of the tissues present. By contrast, the full thickness and wedge
biopsy methods are more reliable due to the large volume of cells
harvested. These methods, however, require a more invasive operation
than the needle biopsies.
Once the biopsy sample has been collected
the tissue is placed into a container with a preservative such as
formaldehyde. This keeps the cells intact while the specimen is
transported to the laboratory. A veterinary pathologist will then
take thin slices of the tissue, apply a stain and then evaluate
the cells under a microscope. Since most diseases leave a characteristic
foot print on the cells the pathologist can thereby
recognize the disease and make a diagnosis. In addition, information
such as the future course of the disease (prognosis), a grading
system for malignancies and whether or not the margins of the sample
are clean or not will be reported. Most laboratories
are able to process a biopsy sample within 3-5 days for a reasonable
cost.
With the relative safety of todays
anesthetics combined with technologically advanced tools, such as
the ultrasound and flexible fiberoptic scopes, the risk benefit
ratio is clearly in favor of obtaining the biopsy sample. The accuracy
of a biopsy as a test is usually good to excellent if the tissue
is representative of the problem. Your veterinarian will be able
to advise you on when a biopsy is indicated and can often perform
the procedure within the hospital on short notice. In most cases
the after care is minimal and so is any discomfort.
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