The Rat Fan Club

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

Rat Fan Club
857 Lindo Lane
Chico, CA 95973
(530) 899-0605 ratlady@ratfanclub.org