How to Do a Rat Autopsy
by Debbie “The Rat Lady” Ducommun
Much
is known about disease in lab rats, but little is known about disease in
companion rats. Unfortunately, few
rat owners choose to have autopsies done on their rats. Even when the cause of death seems
obvious, say respiratory disease, the real cause may be different. For example, I’ve found that heart
disease often mimics respiratory disease in rats. I try to do at least a gross autopsy
(which is just looking at the organs and takes only a few minutes) on all rats
that I can. I’d be happy to
do a gross autopsy on your rat if you’d like to send me the remains. I can then bury them here, or return the
body to you.
I
know that some of you don’t like the idea of having an autopsy done on
your rat, but please do consider it.
Once your rat has passed on, the remains are not your rat any longer,
only the vehicle that your rat occupied.
If your rat dies of an unknown cause, I urge you to have an autopsy done
and let me know the results so we can gather more information on disease in
rats. It’s possible that an
autopsy can later help another rat who is having the same symptoms.
Some
vets may be willing to do a gross autopsy for free. However, in some cases to really know
the true cause of death, organ tissue samples must be sent to a pathology lab
which can be fairly expensive. Some
labs offer a special low price for low-income people, so ask your vet about
this possibility. If you plan to
have an autopsy done, and cannot get your rat’s body to the vet right
away, do not put it in the freezer, which will damage the cells. Instead, after sealing it in a zip-lock
bag, place it in the refrigerator.
Then get it to your vet as soon as possible.
Doing
a rat autopsy is very easy. Of
course, I understand that most of you are not going to want to do an autopsy,
especially on your own rat, but I want to make the information available. Perhaps the information will be useful
to your vet, or perhaps you have a friend with a scientific bent who would be
willing to do it for you. The
drawing I have included is fairly rough.
I hope to add photos soon.
A
gross autopsy consists of examining all the organs to see if their size, color,
shape, and texture is different from normal. In most cases, this will reveal the
major cause of death. In some
cases, tissue pathology will be necessary to identify the major cause of death,
or contributing causes. For this,
small samples of all the organs are needed. It is best if the samples are placed in
a formalin solution (ask your vet), but if necessary they can be placed in
rubbing alcohol. The samples should
be taken gently to avoid damaging them.
Tools
There
are only a few tools you need to do a rat autopsy. You need a pair of sturdy scissors with
a sharp point, a pair of tweezers or forceps, a pair of needle-nose pliers, and
gloves. For measuring, you’ll
need a ruler marked in mm.
It’s a good idea to take notes during the autopsy,
otherwise it can be difficult to remember everything. Here are some terms which are useful in
describing an autopsy: lesion—a tissue change; mass—a tumor;
textures—brittle, caseous (cheese-like), firm, friable (easily broken up),
gelatinous, gritty, hard, rubbery, soft, watery; severity—minimal, mild, moderate, marked.
Starting the Autopsy
First
examine the whole body and feel for abnormal lumps or lesions. Next I recommend checking to see if
there was a pituitary tumor. This
is the most unpleasant part of the autopsy, but we do not have any good
statistics on the incidence of this disease in pet rats, so it would really
help to gather this information.
There may be a tumor present even if it was not yet causing symptoms.
Lay
the remains on the belly. With the
scissors, cut the skin on the top of the head from between the eyes to between
the ears. Spread the skin apart
until you can see the top of the skull.
Place the pliers on either side of the eye sockets and crush the bones
between the eyes. With the tweezers
or forceps, start to remove the pieces of bone from the eyes to the back of the
skull. Gently insert the tool under
the bones to lift and break them up.
Once you reach the large bones forming the top of the braincase, work on
one side at a time. Apply pressure
to get them to separate in the middle and break on the sides so they lift up
like the top of a cardboard box.
This will expose the brain.
Gently slide the tweezers or forceps under the front of the brain, lift
it up, and remove it. It helps if
you turn the body on its side to take advantage of gravity. If a pituitary tumor is present, it will
appear as a dark red blob in the center of the brain cavity. If there is no tumor, the bottom of the
cavity will feature two ridges. I
then replace the brain, fold the bones back in place, and pull the skin back to
cover them.
Turn
the body over on its back. To open the abdomen, start cutting at the lower portion. You need to cut through both the skin
and muscle. Make the incision as
long as possible. Examine all the
organs, referring to the drawing for their locations and normal color. To check the texture of a tissue, cut it
open. When you have more experience it will be easy to see abnormalities in the
organs. Check for tumors and note
the location, appearance and size.
Fluid in the abdominal cavity is usually due to cancer, congestive heart
failure, or long-standing liver disease.
To
open the chest, continue to cut as far forward as you can, slightly to the side
of center to avoid the sternum. Cut
through the ribs and spread them open.
Observe the heart in place, and then remove it. Measure the length and width. Cut it in half longitudinally to measure
the width of the left ventricle and the thickness of its walls. Examine the lungs and note any
abnormalities.
When the
autopsy is finished, the incisions can be sutured closed if desired.
Organ Usual
Abnormalities Possible
Disease
Large intestines
redness
inflammation.
(Depending
on length of time since death, may be bloated due to decomposition.)
Small
intestines redness
inflammation
Uterus
(unspayed female) redness,
swelling, pus infection,
typically mycoplasma
Seminal
vesicles yellow
rubbery matter prostate
disease?
(unneutered male-neutering causes them to shrink to 1/3)
Prostate
(male)
enlarged prostate
disease
Bladder overly
full urinary
blockage
Kidneys speckled,
grayish pink, rough degeneration
Spleen
enlarged non-specific
sign
Liver enlarged,
spots, swollen infection,
degeneration
(Speckling
may occur due to decomposition)
Stomach empty poor
appetite
bloated with air respiratory
distress
Heart,
exterior enlarged dilated
cardiomyopathy
Heart,
interior thick
walls hypertrophic cardiomyopathy
Lungs expanded
and enlarged emphysema
“raspberry” texture mycoplasma
large abscesses mycoplasma
spots of pus, mottling pneumonia
dark red pneumonia, shock

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