October 2026
A common story goes like this: a family notices their female guinea pig is losing hair on both sides of her body. She isn't scratching, she's eating, and she seems fine otherwise, so it gets chalked up to age or a skin problem. Very often, the real cause is ovarian cysts. If you share your home with a sow, they're one of the health problems most worth knowing about.
Ovarian cysts are fluid-filled sacs that form on or near the ovaries. Cystic ovarian disease is very common in intact female guinea pigs, it becomes more likely with age, and it often affects both ovaries.
Not all cysts are the same, and the difference matters for treatment. The most common type comes from a leftover structure near the ovary. These cysts don't produce hormones and don't respond to hormone treatment. Follicular cysts form when an egg follicle fails to release, and these can produce hormones, which is what causes the skin and behavior changes. They may respond to medical treatment. A third type is rare.
Some cysts stay small and cause no trouble. Others grow large, press on nearby organs and make a sow uncomfortable. Female guinea pigs can also develop other reproductive problems, such as uterine disease and tumors.
Hair loss on both flanks, usually without itching, is the classic sign. You may also notice a larger or rounder belly, crusty or thickened nipples, behavior changes such as mounting or irritability, a reduced appetite, weight loss, or discomfort when she's picked up. Some sows have bloody vaginal discharge or what looks like blood in the urine.
Many of these signs overlap with bladder problems, which are also common in guinea pigs. And some sows show nothing on the outside until the cysts are quite large, which is one more reason regular wellness exams matter.
Sometimes I can feel enlarged ovaries during an exam, but ultrasound is the best tool to confirm cysts, judge their size and check the uterus at the same time. X-rays, bloodwork and urine tests help rule out other causes such as bladder stones. The only way to know the exact type of cyst is to examine the tissue under a microscope after it's removed.
Spaying, which removes the ovaries and sometimes the uterus, is the definitive treatment, especially if the uterus is also affected. The outlook after surgery is excellent, and most sows have complete resolution of their signs. I perform guinea pig spays and will talk with you about the best surgical approach for your pig.
For some guinea pigs, especially those who aren't good anesthetic candidates, hormone medication can help, but mainly for follicular cysts. Because the most common type doesn't respond, results vary and ongoing monitoring is needed. A cyst can also be drained with a needle under ultrasound guidance. That gives temporary relief, but cysts often refill within days to weeks.
We'll weigh these choices together based on your guinea pig's age, health, and the size and type of the cysts.
Spaying a healthy younger female before problems develop prevents ovarian cysts and lowers the risk of other reproductive diseases. It also lets sows live safely with neutered males. Neutering boars prevents unwanted litters and may reduce some hormone-driven behaviors, so ask whether it makes sense for your household.
After surgery, keep your guinea pig on soft, clean bedding such as fleece or towels, with a hide to retreat to and food and water close to its entrance. Offer hay, fresh vegetables and their usual pellets right away. Make sure she's eating and producing normal droppings, and give pain medication exactly as directed. Success is a guinea pig who is eating, exploring and chatting again.
Call the same day if your guinea pig is not eating at all or has stopped producing droppings, or if an incision is swollen, red or discharging after surgery.
Book a prompt visit for hair loss on her sides, a growing belly, bloody discharge or blood in the urine, eating less or weight loss.
Dr. Logan Kopp, DVM, DABVP (Exotic Companion Mammal Practice), is Nashville's guinea pig specialist and treats ovarian and other reproductive problems in guinea pigs at Priest Lake Veterinary Hospital. Call (615) 361-4646 to schedule an exam or spay consultation.
This article is general information, not medical advice for your pet. Reading it doesn't create a veterinarian-client-patient relationship (VCPR). Please talk with your own veterinarian before making changes to your pet's care.