You are here:

Rabbits/Does My Rabbit Most Likely Have A Tumor?


QUESTION: Dear Dr. Krempels,

I just took my rabbit to the vet yesterday, and I got some input from our vet, but I would like to run it by you and see what you think. Sorry if this message is long, I just want you to get the full details.

So, my rabbit started developing this rapid breathing 3 weeks ago. The first week, she was breathing rapidly for 2 days straight, but it went away. Two weeks later, it came back, and she's been breathing like this for several days. On the third-fourth day with her like this, I took her to the vet.

During the physical examination, the vet asked me if her attitude has been the same, her eating habits, pooping/urine is normal/the same. To that, I said yes, because my rabbit acts completely like her usual self. She then checked my rabbits paws to see if my rabbit has been wiping her nose, checked her eyes, felt her body, and listened to her stomach and heart. Two x-rays were done as well.

In conclusion, the vet told me there's good news and bad news. The good news is that my rabbit doesn't seem to have any breathing problem, she's not sick, doesn't have heart disease, and it doesn't look like its pneumonia or anything like that. All in all, my rabbit's in fine health aside from the breathing. What's left is that she could possibly have a tumor on her adrenal glands, which may cause her adrenal glands to produce more adrenaline than normal. The other factor is that she thinks my rabbit could have eaten something that is like a stimulant, which causes my rabbit's adrenaline level to increase.

The vet said we wouldn't know until an ultra sound is done that my rabbit has a tumor. IF there is a tumor, she doesn't recommend surgery because it would most likely kill my rabbit. She also concludes that if this was a tumor on the adrenal glands, it would be odd because it's very rare in rabbits.

For now, she told me to let my rabbit stay in the cage for several weeks, and stop feeding her bananas (even though she's pretty sure this isn't the problem) to make sure it's not an environmental factor that's causing my rabbit to be like this. I can take her out, but not let her run around on the floor. The vet also thinks if it's not something she found and ate, it could be what I've been feeding her. This would also be unlikely, because she told me that I've been feeding my other rabbit the same thing for almost three years now, and it has never been a problem. (pellets, hay, veggies, occasionally bananas and apples for snacks).

With the information given, what do you think of my rabbit's state and what the vet told me?

Thank you,

ANSWER: Dear Jay,

Are you sure the vet said adrenal gland tumor?  Because while this is common in animals such as ferrets, it is very uncommon in rabbits, and not likely to cause the fast breathing signs you are observing.  Not impossible, just not very likely.

A far more likely cause is a thymoma, a tumor of the thymus gland, situated just anterior to the heart.  It generally does not metastasize, but as it grows, it impinges on the trachea and lung capacity, causing fast, labored breathing.  It can be diagnosed via radiographs (x ray) or ultrasound.

It is also possible that your rabbit *does* have a lung infection (pneumonia).  We have found that--odd as it sounds--a rabbit with pneumonia does not always present with raspy lung sounds upon auscultation (listening with a stethoscope).  Only on necropsy is the culprit found.  :(

Let's hope this doesn't come to that!

I would suggest you use the veterinary referral list linked here:

and find another rabbit-savvy vet for a second opinion.  The vet you saw does sound as if she did all the right examinations, but sometimes there are cryptic things that another set of eyes might find.

I would certainly ask the vet about taking some rads to see if there is any sign of a thymoma.  Radiographs will also show lung congestion, even if there is no obvious sound of pneumonia.  Thymoma can be treated with radiation therapy and some other protocols.  If your bunny does have a thymoma, please write back and I'll try to help with more information.  Pneumonia requires a completely different set of treatments, of course.  If that's the problem, I'm sure the vet will be able to help.  But always feel free to come back here and ask questions if you think I can help.

I hope this helps, and that your bunny will be fine soon.

Happy holidays,


---------- FOLLOW-UP ----------

QUESTION: Hello again, thank you for you reply.

I was called several days ago by my vet because she wanted to check up on my rabbit. She left me a message asking me how my rabbit is doing and mentioned adrenal gland tumor, again.

You mentioned thymoma and that my rabbit could possibly have this. But, wouldn't my vet have known something if if there was a tumor? After listening to my rabbit's heart, and showing me the x-rays, she told me there's nothing irregular going on inside of my rabbit (aside from the quick breathing). I am assuming radiographs could tell since you mentioned that this could be diagnosed via radiographs or ultrasound.

Actually, I found my vet through the veterinary referral list on I'll try another vet though, so see their input.

I just got off the phone with my vet, I asked her several times about tumor on the thymus, but she was very sure it was not thymoma. She told me through the radiographs, she doesnít see anything there. So, I am not sure if I should believe her or leave it until I go see another vet.
When I mentioned pneumonia, she gave me a lot of reasons why it couldnít be pneumonia. The vet also added that my rabbit wasnít having any difficulty breathing, which is one of the main component with pneumonia. She said someone is going to come back from the holidays, take a closer look at the X-rays, and let me know if they find anything new.

Sheís still confident that my rabbit must have gotten into some stimulant thatís causing her to breathe quickly. And again, she brought up adrenal gland tumor, which is odd because itís very rare. She told me if it did come to this, itís up to my judgement on what I should do. According to her, itís very risky because touching a tumor may cause it to grow more, but also, something about trying to remove it could cause a lot of bleeding.

For now, she told me to just keep making sure my rabbit isnít eating anything funny, and to not let my rabbit near stressful or loud environment because it could cause her breathing to be harsher, which would be bad (her heart could stop or something along those lines).

Please give me anymore input on this when you have the time. Iím very worried about my rabbit, and I am hoping that I am getting accurate diagnosis for her.


Dear Jay,

I would find another rabbit vet for a second opinion.  While the problem might not be pneumonia or thymoma, I find the idea that the rabbit "got into some kind of stimulant" pretty odd.

Bloodwork might help isolate a culprit.  Also be sure to take bun's temperature, in case he's panting because of a fever:

I hope by now your bunny is fine.

Sorry for the delay, caused by a family emergency.  :(



All Answers

Answers by Expert:

Ask Experts


Dana Krempels, Ph.D.


I've lived with companion rabbits for more than 35 years, and consider them members of my family. I can answer any questions about the biology and health of rabbits, from the commonplace to the unusual. But please note:

RULE #1:

Find a rabbit vet at for immediate help, and don't risk your bunny's life by spending time asking questions online! If you can't get in touch with your vet, read these Emergency Sick Bunny Instructions.

If you have found a wild baby rabbit, please read these EMERGENCY INSTRUCTIONS FOR WILD BABY RABBITS and then use this link to FIND A LOCAL WILDLIFE REHABILITATOR who can give you the right advice.

RULE #2:
Help me help you! Please make your subject line informative if you have an urgent question. then LET ME KNOW IN THE SUBJECT LINE so I can give your question highest priority over non-urgent questions. If you don't do this, then I can't guarantee timely assistance!

For all the best, most accurate rabbit health, care and behavior information, visit The House Rabbit Society.


I have been rescuing and rehabilitating domestic and wild rabbits for about 30 years. I have written articles for many rabbit rescue publications, as well as for the veterinary journal, Exotic DVM. I own EtherBun, the internet's largest listserve dedicated to health, care, and behavior of domestic rabbits.

Houserabbit Adoption, Rescue, and Education, Inc. (H.A.R.E., Inc.) president National House Rabbit Society (Board member)

Exotic DVM
Warren Peace (Journal of the House Rabbit Society of Miami)
Various newsletters of the House Rabbit Society, nationwide

Ph.D - Biology
B.S. - Biology
B.A. - English

Awards and Honors
Lightspan Academic Excellence Award for web site on rabbit health and biology

©2017 All rights reserved.