Ovarian Cysts in Guinea Pigs
Extremely common in female guinea pigs — 60-80% of sows over 2 years old develop ovarian cysts. Can cause hormonal disturbances, hair loss, and abdominal discomfort. Easily diagnosed with ultrasound.
Last updated: 2026-05-07
Severity
moderate
When to Act
See Vet Soon
Symptoms & Signs
Bilateral flank hair loss
Symmetrical hair loss on both sides of the abdomen/flanks — the most common presentation.
Pear-shaped abdomen
Distended belly from large cysts.
Nipple enlargement and crusting
Enlarged, crusty nipples from hormonal effects.
Sexual behavior changes
Mounting cage mates, increased aggression, or being mounted more frequently.
Decreased appetite
If a large cyst causes abdominal discomfort or compresses the GI tract.
Behavioral Changes to Watch For
Pets can't tell us what's wrong. These behavioral changes are often the first clues that something is wrong.
🐾 Increased aggression or mounting
Hormonal changes cause dominance behaviors.
What You May Notice:
Your normally peaceful sow is suddenly chasing and mounting her cage mates, or becoming irritable when handled.
Causes & Risk Factors
Causes
- •Functional cystic rete ovarii (spontaneous, non-neoplastic cysts)
- •Cystic rete ovarii is the most common type in guinea pigs
- •Hormonal imbalance — continuous estrus leads to cyst formation
Risk Factors
- ⚠Female guinea pigs (sows) over 2 years old
- ⚠Nulliparous (never bred) — higher incidence
- ⚠60-80% incidence in intact sows over 2 years of age
How It's Diagnosed
- 1Abdominal ultrasound — definitive; reveals fluid-filled cystic structures on the ovaries
- 2Clinical signs — bilateral flank alopecia in a female guinea pig is highly suggestive
- 3Abdominal palpation — large cysts may be palpable
- 4Radiographs — less sensitive than ultrasound for cystic structures
Treatment Options
Ovariohysterectomy (Spay)
The definitive treatment — removes both ovaries and the uterus.
Steps
- 1.Standard ovariohysterectomy under general anesthesia
- 2.Cystic ovaries are removed
- 3.Hospitalization for 1-2 days post-op
- 4.Pain management and supportive care during recovery
Expected Outcome
Complete resolution of hormonal signs. Hair regrowth within 1-3 months.
Precautions
- !Anesthesia risk is higher in guinea pigs than dogs/cats — use an experienced exotic vet
- !Post-op GI stasis is a risk — ensure the sow is eating promptly after surgery
Ultrasound-Guided Cyst Drainage
Less invasive option — percutaneous drainage of cysts.
Steps
- 1.Ultrasound-guided aspiration of cyst fluid
- 2.Sedation required
- 3.Cysts often refill within weeks to months
Expected Outcome
Temporary relief of abdominal distension. High recurrence rate.
Precautions
- !Temporary solution — cysts typically refill
- !Risk of cyst rupture or infection
Hormonal Therapy (hCG Injections)
Human chorionic gonadotropin (hCG) can shrink functional cysts.
Steps
- 1.hCG injections — 2 doses, 7-10 days apart
- 2.Most effective for functional cysts (cystic rete ovarii)
- 3.Response is monitored via ultrasound and clinical signs
Expected Outcome
Variable — 50-70% of functional cysts respond. Neoplastic cysts will not respond.
Precautions
- !Not effective for all cyst types
- !Recurrence may occur
- !Spay provides permanent resolution
Common Medications Used
| Medication | Usage | Important Notes |
|---|
Prevention
- ✓Spay young sows not intended for breeding — prevents ovarian cysts entirely
- ✓Regular wellness exams for female guinea pigs over 2 years
- ✓Monitor for flank hair loss — early sign
When to See a Veterinarian
- ⚠️Hair loss on the flanks of a female guinea pig
- ⚠️Distended or pear-shaped abdomen
- ⚠️Behavioral changes (aggression, mounting)
Frequently Asked Questions
Can my guinea pig live with ovarian cysts without treatment?
Prognosis
Excellent with spay surgery. Complete resolution of clinical signs is expected. Opting not to treat: cysts continue to enlarge, potentially causing abdominal discomfort, GI compression, and poor quality of life.
References
- [1] BSAVA — Manual of Rodents
- [2] Guinea Lynx — Ovarian Cysts
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