Rabbit Mammary Swelling: Mastitis, False Pregnancy, or a Lump?
General guidance — not a diagnosis. When in doubt, call your vet.
What a swollen nipple or mammary lump can mean
Rabbit mammary swelling is a sign, not a diagnosis. Nursing and false pregnancy can change mammary tissue, while infection, cysts, and tumors need different care. You cannot safely identify the cause from a photograph, firmness, or skin color alone. Arrange an examination with a rabbit-experienced exotic veterinarian; seek urgent care if your rabbit seems unwell.
False pregnancy can cause mammary enlargement even without kits. Rabbit pathology guidance describes diffuse enlargement and hyperplasia during pseudopregnancy.[1] A history of nursing or false pregnancy is useful information, not proof that a new lump is harmless.
Clues that help your vet narrow the possibilities
Infection: Septic mastitis can produce warm, firm, red or blue-tinged glands and loss of appetite or depression. Mammary abscesses can occur even without lactation.[2]
Cystic disease: Noninfectious cystic mastitis can also look firm and blue-tinged, sometimes with nipple discharge, while the rabbit otherwise appears well.[2]
Tumors and tumor-like lumps: A pathology study found cysts, benign tumors, and carcinomas among pet-rabbit mammary specimens, sometimes together.[3] Its selected laboratory cases do not tell us the chance that your rabbit's lump is cancer.
A mammary-tumor review also reports affected spayed females.[4] Being spayed should not be used to dismiss a new lump.
What to record and what not to attempt
Before the appointment, note whether your rabbit is spayed, recently bred, nursing, or showing a recurring swelling pattern. Record where the change is, whether it is spreading, and any visible wound or discharge. Take a photograph without restraining your rabbit on its back or repeatedly handling the lump.
Track eating, activity, and droppings. Our guide to smaller or fewer rabbit droppings can help you describe that change. Keep bedding clean and dry and remove sharp surfaces. Do not squeeze, lance, massage, or try to drain the swelling; do not use leftover antibiotics or human pain medicines. Ask the clinic for a specific plan if kits are nursing.
Your veterinarian may recommend culture or needle sampling.[2] Persistent masses may need histopathology.[3]
For related context, see rabbit abscesses. Your veterinarian may also assess reproductive disease; our rabbit uterine cancer guide covers that separate concern.
When to See a Vet
- Seek emergency care now if your rabbit collapses, cannot stand, or is struggling to breathe.
- Contact a rabbit-experienced veterinarian urgently if swelling occurs with refusal of food, markedly fewer droppings, or unusual inactivity.
- Request same-day advice for rapidly enlarging swelling, obvious pain, an open wound, or nipple discharge.
- Arrange a prompt examination for any new or persistent mammary lump, even if your rabbit is eating and acting normally.
For rabbit owners
An article can't ask about your rabbit.
Describe what you're seeing. You'll get a few follow-up questions about your rabbit, then where it lands — vet today, watch closely, or no visit needed — and what to do at home meanwhile.
Frequently Asked Questions
Can a rabbit have swollen mammary glands without being pregnant?
Yes. Pseudopregnancy can enlarge mammary tissue.[1] Tell the veterinarian about the reproductive history rather than assuming pregnancy or infection.
Does blue skin prove my rabbit has mastitis?
No. Both septic and cystic mastitis can have blue-tinged glands.[2] Photograph the change and arrange an examination.
Does a firm lump mean cancer?
No. Rabbit mammary specimens can contain cysts, benign tumors, or carcinomas.[3] Appearance and touch cannot replace testing.
Can a spayed rabbit still have a mammary tumor?
Yes. Mammary tumors have been reported in spayed females.[4] Have a new lump checked.
Should I squeeze the nipple to check for milk or pus?
No. Leave sampling to the veterinarian. Describe any discharge you have already seen without expressing the gland.
What should I do if there are nursing kits?
Tell the clinic immediately that kits depend on the doe. Ask for an explicit feeding and nursing plan; do not improvise separation or a milk-replacer schedule.
References
- Bradley AE et al. International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8544166/
- Chen S, Quesenberry KE. Rabbits. Saunders Manual of Small Animal Practice. 2006 issue; PMC display date 2009. https://pmc.ncbi.nlm.nih.gov/articles/PMC7158356/
- Schöniger S, Horn L-C, Schoon H-A. Tumors and tumor-like lesions in the mammary gland of 24 pet rabbits: a histomorphological and immunohistochemical characterization. 2014. https://pubmed.ncbi.nlm.nih.gov/23892377/
- Schöniger S et al. A Review on Mammary Tumors in Rabbits: Translation of Pathology into Medical Care. 2019. https://pmc.ncbi.nlm.nih.gov/articles/PMC6826878/