A rabbit with a swollen belly, reduced fecal output, and loss of appetite may have uterine hydrometra — an accumulation of fluid inside the uterus. It is most common in older unspayed female rabbits and can rapidly progress to life-threatening uterine rupture or sepsis. Spaying is both the treatment and the prevention.
Last reviewed: June 2026
What Is Uterine Hydrometra in Rabbits?
Uterine hydrometra is the accumulation of watery, non-infected fluid within the uterine lumen in female rabbits. It is distinct from pyometra (pus accumulation from bacterial infection) and mucometra (mucus accumulation), though all three can occur in the same rabbit — the lumen fluid may transition from clear to infected over time if the cervix eventually obstructs drainage, as described in Quesenberry and Carpenter's Ferrets, Rabbits and Rodents.
Hydrometra in rabbits most commonly arises from:
- Cystic endometrial hyperplasia — hormonally driven proliferation of the uterine glands, leading to a fluid-secreting cystic endometrium; the dominant reproductive pathology of intact does over 3 years of age
- Endometrial polyps or adenocarcinoma — both can obstruct the uterine lumen and cause fluid accumulation; uterine adenocarcinoma occurs in up to 50–80% of intact does over 5 years of age in some studies
- Cervical stenosis — scarring or congenital narrowing prevents uterine drainage
Because rabbits do not show early, obvious estrous bleeding and have concealed anatomy, uterine disease is often far advanced before owners notice anything unusual.
Signs of Uterine Hydrometra in Rabbits
- Gradual abdominal distension — the rabbit's belly enlarges from below; may feel fluid-filled when gently palpated
- Reduced fecal output — the enlarged uterus compresses the GI tract, reducing intestinal motility; cecotrope consumption may decrease
- Anorexia and lethargy — especially as the fluid volume grows and abdominal discomfort increases
- Increased urination or straining to urinate — the enlarged uterus presses on the bladder
- Bloody vaginal discharge — if concurrent uterine adenocarcinoma or endometrial polyps are present; any vaginal discharge in a rabbit warrants evaluation
- Weight loss despite a large belly — the rabbit loses body mass while the uterus enlarges
- Respiratory difficulty — in severe cases, massive uterine enlargement restricts diaphragmatic movement
- Sudden deterioration — if uterine rupture occurs, septic peritonitis develops rapidly
Diagnosis
Your exotic vet will use:
- Abdominal palpation — a fluid-filled uterus is often palpable as a soft, fluctuant midabdominal or caudal abdominal structure in a doe rabbit
- Abdominal radiographs — reveals a soft-tissue midabdominal mass displacing intestinal loops; useful for estimating size
- Abdominal ultrasound — best diagnostic tool; shows fluid-filled uterine horns, uterine wall architecture, and any echogenic masses suggesting adenocarcinoma or polyps; also evaluates for peritoneal fluid suggesting rupture
- CBC and chemistry panel — assesses anemia (common with chronic uterine disease), kidney function, liver enzymes, and infectious markers; baseline before surgery
- Chest radiographs — pulmonary metastasis occurs in approximately 25% of does with uterine adenocarcinoma at presentation; staging is essential before surgery
The AEMV Pet Care Guides, 2024 recommend complete reproductive tract evaluation in all intact does over 2 years of age.
Treatment
Ovariohysterectomy (OVH) is the definitive treatment. The entire uterus and ovaries are removed. Even very large hydrometras can be surgically managed safely with an experienced exotic vet and a rabbit-skilled anesthesia team.
Key perioperative considerations:
- Rabbits are obligate nasal breathers; anesthetic protocols use isoflurane with careful respiratory monitoring
- Gut motility must be supported before, during, and after surgery with syringe feeding, prokinetics (metoclopramide, cisapride), and pain management
- IV fluid support during surgery and recovery
- Recovery is faster and safer when surgery is performed before the rabbit is in a severely debilitated state
All excised uterine tissue should be submitted for histopathology to detect concurrent adenocarcinoma and assess margins.
Prevention: Spaying (OVH) before 2 years of age essentially eliminates the risk of hydrometra, pyometra, and uterine adenocarcinoma in does — the strongest argument for early elective spaying.
When to See a Vet
Call your vet today if:
- Your intact female rabbit's belly looks larger than usual or feels soft and fluid-filled
- Your rabbit is producing fewer fecal pellets or cecotropes than normal
- You see any vaginal discharge — clear, bloody, or otherwise
- Your rabbit's appetite has decreased over the past week
Go to the ER immediately if:
- Your rabbit is not eating at all and the belly is visibly distended
- Your rabbit is in obvious pain — hunched, tooth-grinding, unable to rest comfortably
- Breathing is labored or rapid
- Sudden collapse or unresponsiveness
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Frequently Asked Questions
How common is uterine disease in rabbits? Uterine disease is extremely common in intact does. Uterine adenocarcinoma has been reported in up to 50–80% of intact females over 5 years of age in some populations, as described in Quesenberry and Carpenter's Ferrets, Rabbits and Rodents. Cystic endometrial hyperplasia and hydrometra develop earlier, often by 3–4 years of age. Spaying before age 2 eliminates essentially all of this risk.
Can uterine hydrometra in rabbits be treated without surgery? No effective medical alternative to surgery exists. Hormonal manipulation is not reliably effective and risks exacerbating underlying disease. Drainage alone (aspiration of uterine fluid) without OVH provides only temporary relief and does not address the underlying cause. Surgery is the only option for cure.
What does the fluid in uterine hydrometra look like? The fluid ranges from clear and watery to amber or straw-yellow. If secondary infection has occurred (transitioning to pyometra), it becomes cloudy or purulent. Bloody fluid suggests concurrent endometrial adenocarcinoma or polyps. On ultrasound, hydrometra fluid appears as anechoic (black) fluid within the uterine lumen.
How much does uterine surgery cost for a rabbit? Exotic vet consultation and bloodwork run $100–250. Ultrasound adds $200–400. Abdominal radiographs (including chest staging) cost $150–300. OVH surgery under anesthesia at an exotic practice typically costs $500–1,200. Hospitalization and postoperative care add $200–500. Histopathology is $100–200. Total episode of care is commonly $1,000–2,500. Preventive OVH at a young age costs $300–600 and avoids this significantly more expensive emergency treatment.
What is the prognosis after hydrometra surgery in rabbits? If the uterine disease is benign (hydrometra or cystic endometrial hyperplasia without adenocarcinoma), prognosis after OVH is excellent with full recovery expected. If adenocarcinoma is found and the excision is complete without pulmonary metastasis, survival times of 1–3 years post-surgery are reported. Does with pulmonary metastasis at presentation have a guarded prognosis with a median survival of 6–12 months.
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