home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Cream of the Crop 20
/
Cream of the Crop 20 (Terry Blount) (1996).iso
/
faq
/
ferretv3.zip
/
VETINFO.ZIP
/
SPLENOM.TXT
< prev
Wrap
Text File
|
1996-05-27
|
10KB
|
195 lines
Please note: I am not a ferret expert, and I did not write, nor did I
independently verify, all the information in this file. I have done
my best to include only accurate and useful information, but I cannot
guarantee that what is contained in this file, whether written by me
or by one of the contributors, is correct, or even that following the
advice herein won't be harmful to you or your ferret in some way. For
advice from an expert, you may wish to consult one of several books
available, or, especially in the case of a suspected medical problem,
a veterinarian who is familiar with the treatment of ferrets.
FERRET MEDICAL FAQ -- SPLENOMEGALY
Last modified: 16 Mar 95
Version: 1.3
------------------------------
Subject: CONTENTS
*** Splenomegaly ***
(1) The Mystery of Splenomegaly in Ferrets (Dr. Williams)
(2) Postoperative care for splenectomy (Dr. Weiss)
(3) Ferret Medical FAQ copyright and redistribution information
------------------------------
Subject: (1) The Mystery of Splenomegaly in Ferrets (Dr. Williams)
Written by Dr. Bruce Williams, DVM:
Splenomegaly, or the enlargement of the spleen, is one of the
biggest question marks in ferret medicine today. As a veterinary
pathologist, over 15% of my surgical biopsies from ferrets involve
enlarged spleens. As a ferret owner, I have seen the spleens of
several of my ferrets wax and wane in size over the years. In truth,
one of my ferrets, who is now seven, has had an enlarged spleen for
most of his life.
Fact -- we don't know what causes splenomegaly in the ferret.
There are several theories, and I have come to my own conclusions
(which I'll discuss in a moment), but nobody really knows for sure.
Remember, as compared to dogs and cats, we actually know very little
about ferret disease. While our knowledge about this species grows
daily, it will be many years before we amass the amount of knowledge
about ferrets that we have about more traditional companion animals.
First of all, what does the spleen do? The spleen actually
has several functions. Its most important function is to act as a
filter for the blood, ever sifting the blood for bacterial agents or
evidence of inflammation against which its high population of white
blood cells may mount an attack. Additionally, the spleen may act as
a storehouse for blood - in some species, the spleen holds as much as
15-20% of the total blood volume in reserve, so that it is immediately
available in times of stress. Additionally, the spleen filters out
old red blood cells, which are trapped and subsequently digested by
the white blood cells that live there - the iron in these cells is
reclaimed, and may be used again if necessary, or it may be stored in
the spleen against future needs. Finally, the spleen, in many
species, and especially in the ferret, is where new blood cells, of
both the red and white varieties, may be made, in addition to the bone
marrow. Generally, this process occurs only where there is a greater
than normal need for these cells, (i.e., after hemorrhage, or during
systemic infections.)
All this is fact. Here's another fact: only five percent of the
enlarged spleens that I see in my pathology work are the result of
some type of neoplasm - lymphosarcoma being the most common neoplastic
cause of splenomegaly. By far, the most common cause of splenic
enlargement in ferrets is an accumulation of massive numbers of
developing red and white blood cells (known as "extramedullary
hemtopoiesis") .
What causes splenic hematopoiesis? Well, that's where the
theories begin.
The virus theory. While several facilities have purported that a
virus causes this change, one has never been isolated, and in my
opinion, this theory is yet unproven.
The hypersplenism theory. Several years ago, a case report1 was
published on a ferret with a large spleen, who had a progressively
decreasing blood count and a large spleen. When the spleen was
removed, the blood count stabilized. The theory arose that a
malfunctionof the spleen was responsible for excessive destruction
of red blood cells. The term "hypersplenism" was applied to this
phenomenon, after a condition in humans that bears some
resemblance. However, this was an isolated case, and has not been
reported again.
My theory, (well, it IS my article....) This is not the result of
a formal study- this is simply my opinion, based on looking at
hundreds of cases of splenomegaly with associated clinical data. We
know that the extramedullary hematopoiesis arises as a result an
increased demand for either red or white blood cells, and there is
no reason not to believe that this is the case in ferrets. But
relatively few of these animals have evidence of anemia or recent
hemorrhage -- this leaves us with the more likely possibility of
chronic smoldering infections resulting in an increased demand for
blood cells. Well, I certainly see my share of gastroenteritis,
and renal infections, but that still leaves a very large portion of
animals with enlarged splens from a yet undetermined cause.
However, when you go back and look at the ferrets which had
enlarged spleens at autopsy, a large percentage of them have
evidence of chronic gastritis due to infection by Helicobacter
mustelae. Helicobacter is a very common asymptomatic bacterial
infection in ferrets which, over time, causes a marked inflammatory
response in the stomach and associated lymph nodes. In fact, it is
the rare animal over 4 years of age that does not have microscopic
evidence of Helicobacter infection. I believe that chronic
infection in ferrets due to gastric Helicobacter infection is
responsible for a large number (not all) cases of splenomegaly in
the ferret.
Now let's look at another, probably more important issue - what
we should do about enlarged spleens. Ferrets certainly do not need
their spleens to live - they tolerate splenectomy very well, and it is
commonly done. But rather than take out every big spleen we see, we
need to set some criteria as to when to remove them and when to leave
them in. Ideally, we would like to leave them all in, but for various
reasons, we are not always able to.
Certainly, all spleens with lymphosarcoma or any other type of
neoplasm should come out immediately. Veterinarians can tell when a
spleen has a neoplasm in it without taking it out - they can aspirate
cells from it with a needle and light anesthesia, or take a small
piece of it during exploratory abdominal surgery. Qualified
veterinary pathologists with experience with ferrets can then look at
the cells in the biopsy to determine whether they are compatible with
lymphosarcoma, other neoplasms, or are more consistent with a
proliferation of immature blood elements.
In situations where a neoplasm is not present, the pros and cons
of splenectomy should be discussed with your veterinarian. If an
animal simply has a large spleen, but shows no signs of illness or
discomfort, it is safer for the animal to leave it in. However, if
the animal shows signs of discomfort, such as lethargy and a poor
appetite, or a decrease in activity, then the spleen may come out.
Finally, if the spleen is especially large, and the animal is very
active, there is a risk of splenic rupture, and once again,
splenectomy should be considered.
As of yet, the jury's still out on big spleens in ferrets.
However, we do know that all of these cases should be investigated by
your veterinarian, and appropriate steps taken to insure your pet's
health and well-being.
Bruce Williams, DVM
williamb@email.afip.osd.mil
------------------------------
Subject: (2) Postoperative care for splenectomy (Dr. Weiss)
Written by Dr. Charles Weiss, DVM:
Although splenectomy is an abdominal surgery it is straightforward.
When isofluorane is used for anesthesia the ferrets wake up quickly
after surgery and can usually go home the same night (if