Rabbit Mammary Swelling: Enlarged Mammary Glands, Milk or Breast Lumps

Rabbit mammary swelling can happen for several different reasons, and the cause matters because treatment options vary. In female rabbits, one common explanation is pseudopregnancy, where hormone changes trigger nest building, fur pulling, and mammary enlargement even though the rabbit is not truly pregnant. Lactating does can also develop milk buildup or inflammation in the glands.

Another important cause is mastitis, which is inflammation and often infection of the mammary tissue. Affected glands may look red, feel warm, become firm or painful, and may produce abnormal discharge rather than normal milk. Rabbits with mastitis can also seem tired, eat less, or become dehydrated if the infection is more serious.

Some rabbits develop cystic mammary changes or abscesses, which can feel like soft or firm lumps under the skin. In intact female rabbits, mammary swelling can also be linked with disease in the reproductive tract. Unspayed females, especially those older than 3 years, have a well-known risk of uterine adenocarcinoma, and mammary cysts or growths may occur alongside uterine disease.

Finally, mammary tumors are possible, particularly in intact females. A lump is not automatically cancer, but a persistent, enlarging, or irregular mass should be checked by your vet. Rabbits are prey animals and often hide illness, so even a rabbit acting fairly normal can still have a meaningful problem.

A small, nonpainful swelling in a bright, eating rabbit may allow for short-term monitoring while you arrange a veterinary visit, especially if your rabbit is showing signs of pseudopregnancy such as nest building or fur pulling. Even then, it is wise to book an appointment soon, because mammary swelling in rabbits can overlap with infection, cysts, and tumors.

See your vet within 24-48 hours if you notice a new lump, repeated swelling, asymmetry between glands, cloudy or bloody discharge, or if your rabbit is an intact female. Prompt evaluation is also important if there is blood in the urine, because pet parents may think it is urinary bleeding when it can actually be reproductive disease.

See your vet the same day if the gland is hot, red, very firm, painful, leaking pus, or if your rabbit is eating less, hiding, grinding teeth, acting weak, or producing fewer droppings. Rabbits can decline quickly when pain, infection, or reduced food intake are involved.

See your vet immediately if your rabbit stops eating, has trouble breathing, becomes severely lethargic, collapses, or the swelling rapidly enlarges or opens. Those signs can point to severe infection, shock, or advanced disease and should not be watched at home.

Your vet will start with a hands-on exam and a careful history. They will ask whether your rabbit is spayed, whether she could be pregnant, whether there has been nest building or fur pulling, how long the swelling has been present, and whether there is discharge, pain, appetite change, or blood seen around the urine. In rabbits, those details help narrow the list from hormonal swelling to infection, cysts, or cancer.

Depending on the exam, your vet may recommend a fine-needle aspirate or sample of discharge, bloodwork, and imaging such as radiographs or ultrasound. Imaging is especially helpful in intact females because mammary changes can occur along with uterine or ovarian disease. If infection is suspected, culture and sensitivity testing can help guide antibiotic choices.

Treatment depends on the cause. Options may include pain control, supportive care, careful wound management, antibiotics when infection is confirmed or strongly suspected, and surgery for recurrent cystic disease, abscessed tissue, or mammary masses. In some rabbits, your vet may recommend spay surgery at the same time if the rabbit is intact and reproductive disease is a concern.

If a mass is removed, sending tissue to a lab for histopathology is often the best way to learn exactly what it is. That information helps your vet discuss prognosis, whether more treatment is needed, and how closely your rabbit should be monitored going forward.

Do not squeeze, massage, or try to drain a swollen mammary gland at home. That can worsen pain, spread infection, or damage tissue. Keep your rabbit in a clean, dry enclosure with soft bedding, and watch closely for appetite, water intake, droppings, posture, and activity level. A rabbit that eats less because of pain can develop gut slowdown quickly.

If your vet has prescribed medication, give it exactly as directed and finish the full course unless your vet tells you otherwise. Check the area at least once or twice daily for increasing redness, heat, discharge, skin breakdown, or a lump that seems larger. If your rabbit is recovering from surgery, follow your vet's instructions for incision checks, activity restriction, and feeding support.

Offer normal grass hay at all times and keep your rabbit's routine as calm as possible. Stress can reduce eating. If your rabbit is not eating well, is producing fewer droppings, or seems painful despite treatment, contact your vet promptly rather than waiting.

Long term, one of the most important preventive discussions is whether spaying is appropriate for your rabbit. Spaying does not treat every cause of mammary swelling, but it can reduce the risk of serious reproductive disease in intact female rabbits and may be part of the overall plan your vet recommends.