Mouse Rectal Prolapse: Red Tissue at the Anus and Urgent Care
General guidance — not a diagnosis. When in doubt, call your vet.
Exposed tissue needs prompt care
A red or pink cylinder of tissue protruding from a mouse's anus may be rectal prolapse. This is not something to watch for several days or push back at home. Call an exotic-animal veterinarian promptly, keep the mouse quiet and the tissue protected from contamination, and prevent cage mates from chewing or grooming the area.
Observe without pulling. Prolapsed tissue is attached and may appear moist, swollen, or inflamed. Merck Professional describes rectal prolapse across animals as one or more rectal layers protruding because of persistent straining associated with intestinal, anorectal, or urinary or reproductive disease [1]. An examination is needed to confirm what tissue is exposed and why the mouse is straining.
Why a mouse may prolapse
Prolapse is a consequence, not the complete diagnosis. Severe enteritis, intestinal parasites, rectal disease, urinary obstruction, cystitis, reproductive problems, and colitis are among the broad causes of persistent straining described in animals [1]. In pet mice specifically, Merck Professional notes that rectal prolapse from straining may be the only indication of pinworm infestation [2]. That does not mean every prolapse is caused by worms, and it does not justify using an over-the-counter dewormer without testing and veterinary direction.
Tell the clinic about loose stool, reduced or absent droppings, blood, urinary effort, pregnancy or a recent litter, and appetite change. If loose stool is present, the mouse diarrhea pattern and duration may help the veterinarian prioritize testing. A mouse that has stopped chewing normally may also have a separate painful problem such as overgrown teeth, so report food selection and weight change rather than assuming all signs come from the prolapse.
Laboratory evidence must be kept in context. One surgical report treated rectal prolapse in 12 laboratory mice and described spontaneous cases, genetically modified animals, infection with organisms such as Citrobacter, and experimental colitis models [3]. Those settings do not establish which causes are common in household pet mice or predict an individual pet's outcome. The report does show that treatment involved anesthesia, reduction, and a purse-string suture—not a home maneuver [3].
What to do before the appointment
Move the mouse to a clean, simple carrier or hospital enclosure where you can see droppings and urine. Use soft, low-dust paper bedding or clean towels that will not adhere to exposed tissue. Separate a cage mate if it is licking, biting, or climbing on the affected mouse, but keep the surroundings calm and familiar.
Do not scrub the tissue, apply antiseptic, use hemorrhoid cream, sprinkle sugar on it, or attempt reduction. Merck's professional treatment description includes veterinary lavage, reduction under anesthesia, and surgery when tissue is not viable or cannot be reduced [1]. Those details explain why prompt assessment matters; they are not instructions for an owner. The surface can become ulcerated, dark, hard, and necrotic as damage progresses [1].
If the tissue is collecting debris during transport, ask the clinic by phone how to protect it. Do not delay departure while searching for supplies. Avoid force-feeding or syringing water into a weak or struggling mouse. Keep familiar food and water accessible if the mouse can use them normally.
Observe breathing before handling. A concurrent mouse respiratory infection or other breathing problem changes transport and stabilization priorities. Tell the clinic immediately if breathing is labored, because stressed handling can be dangerous in a debilitated mouse. Bring a photo taken without manipulating the tissue, notes on stool and urine output, current medications, diet, and the time the protrusion was first seen.
What the veterinarian may assess
The veterinarian will identify whether the protruding structure is rectum or another tissue and judge color, swelling, contamination, injury, and viability. The exam may be staged to minimize stress. Fecal testing, imaging, urinalysis, or reproductive evaluation may be selected according to the history rather than applied to every mouse.
Treatment must address both the exposed tissue and the cause of straining. Viable tissue may sometimes be cleaned and replaced under anesthesia; damaged or nonviable tissue can require surgery [1]. After treatment, the team will monitor defecation and recurrence and provide species-appropriate pain control and medication directions. Follow those directions exactly and report renewed straining or protrusion promptly.
When to See a Vet
- Pink, red, purple, gray, or dark tissue is protruding from the anus.
- The mouse is repeatedly straining, bleeding, passing little or no stool or urine, or has a swollen abdomen.
- Exposed tissue is drying, contaminated, injured, chewed, or changing color.
- The mouse is weak, cold, not eating, or breathing with visible effort.
For mouse owners
An article can't ask about your mouse.
Describe what you're seeing. You'll get a few follow-up questions about your mouse, then where it lands — vet today, watch closely, or no visit needed — and what to do at home meanwhile.
Frequently Asked Questions
Can I push a mouse's rectal prolapse back in?
No. The tissue can be injured, contaminated, or mistaken for another structure, and reduction may require anesthesia. Keep handling minimal and arrange prompt exotic-animal veterinary care.
What does rectal prolapse look like in a mouse?
It may look like moist pink or red cylindrical tissue attached at the anus. Swelling, ulceration, darkening, or hardening can develop as damage progresses [1]. Do not pull on it to check.
Are pinworms always the cause?
No. Merck Professional notes that prolapse from straining can be the only indication of pinworms in mice, but intestinal, urinary, reproductive, rectal, and other problems can also cause straining [2]. A veterinarian should choose the tests.
Can I put cream, sugar, or antiseptic on the tissue?
Do not apply a product or home remedy unless the receiving veterinarian specifically directs it. Avoid scrubbing and do not attempt reduction; use clean transport housing and leave promptly.
Should I separate the affected mouse?
Separate cage mates that lick, bite, or traumatize the tissue. A clean temporary enclosure also makes output easier to monitor, but avoid unnecessary isolation and handling stress.
Will a prolapse go away on its own?
Do not rely on that. Exposed tissue can swell, ulcerate, and lose viability, while the underlying cause of straining remains. Earlier veterinary assessment gives the clinician more options.
What should I tell the veterinarian?
Report when the tissue appeared, its color change, stool and urine output, appetite, weight trend, recent diarrhea, pregnancy or litter history, cage-mate behavior, and all medications. A photo can help if it does not delay travel.
References
- Gallagher A. Merck Veterinary Manual, 2025 — Rectal Prolapse in Animals. https://www.merckvetmanual.com/digestive-system/diseases-of-the-rectum-and-anus/rectal-prolapse-in-animals
- Frohlich J. Merck Veterinary Manual, 2026 — Mice and Rats as Pets. https://www.merckvetmanual.com/exotic-and-laboratory-animals/rodents/mice-and-rats-as-pets
- Uchihashi M et al. Journal of the American Association for Laboratory Animal Science, 2015 — Surgical Correction of Rectal Prolapse in Laboratory Mice. https://pubmed.ncbi.nlm.nih.gov/26442289/