Uterine adenocarcinoma and other reproductive tract tumors are common in intact female guinea pigs over 3 years old. Vaginal bleeding outside of estrus, a distended abdomen, and palpable masses are classic signs. Early ovariohysterectomy is often curative; advanced disease with metastasis carries a guarded prognosis (Quesenberry & Carpenter, Ferrets, Rabbits, and Rodents, 4th ed., 2021).
Last reviewed: June 2026
Common Reproductive Tumors
Uterine adenocarcinoma is the most common malignant tumor of the reproductive tract in older intact sows. Other lesions include uterine leiomyomas (benign), ovarian cysts (very common, often hormone-active), and mammary tumors. The same sow may have more than one of these at once. Risk rises sharply after age 3, and intact sows over 5 have substantial risk.
Signs
The earliest and most specific sign is blood in the bedding or on the perineum outside of estrus — guinea pigs do not normally have visible vaginal bleeding. Other signs include a distended or pendulous abdomen, palpable mass on gentle abdominal exam, weight loss, decreased appetite, and progressive lethargy. Ovarian cysts often cause symmetric flank fur loss and behavior changes from hormonal effect.
Diagnosis
Abdominal ultrasound is the most useful test — it differentiates uterine masses, ovarian cysts, and other abdominal disease. Chest x-rays check for metastasis (pulmonary spread changes the prognostic conversation). Bloodwork screens for anemia, infection, and organ function before anesthesia. Definitive diagnosis is histopathology after ovariohysterectomy.
Treatment
Ovariohysterectomy by an experienced exotic vet is the treatment of choice. Surgical mortality at experienced centers is typically under 5 percent. If the cancer has not spread, surgery is often curative, with reported long-term survival in the majority of cases. If pulmonary metastasis is present at diagnosis, prognosis drops sharply and palliative care becomes the focus. Pain control with meloxicam and buprenorphine is essential, as described in Carpenter's Exotic Animal Formulary.
Prevention
Routine ovariohysterectomy in young sows prevents uterine cancer, ovarian cysts, and pyometra. Many exotic vets recommend spaying around 4 to 6 months of age. The 2024 AEMV Pet Care Guides, 2024 outline elective surgery considerations and preventive husbandry. Older intact sows benefit from annual abdominal palpation and screening ultrasound starting around age 3.
When to See a Vet
Call your vet today if:
- Blood in bedding or on the perineum
- Distended or asymmetric abdomen
- Symmetric flank fur loss in an intact sow (suggests ovarian cyst)
- Weight loss or decreased appetite in a sow over 3 years old
- Palpable abdominal mass
Go to the ER immediately if:
- Severe lethargy or weakness with abdominal distention
- Heavy ongoing vaginal bleeding
- Pale gums, cold ears, or collapse
- No fecal pellets for 12 hours plus abdominal distention
- Sudden onset breathing difficulty (possible metastasis or large mass)
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Frequently Asked Questions
Should I spay my guinea pig?
Elective ovariohysterectomy in young sows prevents the common reproductive tumors and cysts seen in older intact females. Many exotic vets recommend spaying at 4 to 6 months. The procedure has higher anesthetic risk than in dogs or cats, so use a board-certified exotic surgeon or a vet with high case volume.
How much does surgery cost for guinea pig uterine cancer?
Exotic vet exam typically runs $80 to $200, abdominal ultrasound is $250 to $500, and chest x-rays are $150 to $400. Ovariohysterectomy at an exotic practice ranges $600 to $1,800. Hospitalization for complicated cases adds $500 to $2,000. Catching disease early via screening ultrasound is dramatically cheaper than surgery on a debilitated sow.
How long will my guinea pig live after surgery?
If the tumor is removed before metastasis, many sows live a normal lifespan (typically 5 to 7 years total). With pulmonary metastasis at diagnosis, median survival is only weeks to months and the focus shifts to palliative care.
Can blood in the bedding be from something else?
Yes. Urinary tract infection, bladder stones, and bladder tumors can all cause hematuria. The presence of blood needs prompt exotic vet exam to distinguish source — urine versus reproductive tract. Imaging is usually needed.
Are ovarian cysts dangerous?
Ovarian cysts are very common in older intact sows and may not be malignant, but they often grow large enough to cause discomfort, alter behavior, and reduce appetite. Treatment is ovariohysterectomy. Drainage with a needle is sometimes done short-term but cysts almost always recur.
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