While ovarian tumors are relatively common in mares, ovarian cysts are not. However, these two types of ovarian growth are generally subject to the same treatment -- surgical removal. If one ovary is removed, your mare can still conceive a foal with an egg released from the remaining ovary.
Unlike other complications of the mare's reproductive system, ovarian cysts often do not cause noticeable pain in the animal unless they become quite large. If that's the case, symptoms resemble those of ovarian tumors, including colic and back pain. Generally, ovarian cysts are discovered when a mare fails to get in foal. Ultrasound testing reveals the cyst on the ovary. In horses, the most common type of ovarian cyst is the cystadenoma, which occurs on only one of the ovaries. On the ultrasound, your veterinarian might see more than one cyst on the affected ovary.
Because cystadenomas are usually benign and slow-growing, and because they don't bother the mare, you can take time to decide whether to remove the ovary as part of treatment. If it's important that you breed your mare or if she's in discomfort, the surgery should come sooner rather than later. If breeding her isn't that big of a deal, you can take a wait-and-see approach. If you decide to have the ovary removed, the right surgical procedure for your mare depends on her disposition and ovary size, and on the expertise of your veterinarian.
If your mare is a relatively calm animal, your vet might opt for a standing surgery. The mare receives sedation along with an epidural anesthesia, and the surgeon removes the ovary via the vagina or through an incision in the flank. If done through the vagina, the mare can heal relatively rapidly, but complications are common. These include infections, hemorrhage and vaginal adhesions. An alternative to standing surgery is surgery under general anesthesia, performed at a veterinary hospital. In this case, the affected ovary is removed via an incision in the abdomen. This method can have similar complications and a much longer recuperation time.
Laparoscopic removal of the ovary is easier on your mare, but you must have a veterinary surgeon capable of using laparoscopic equipment. In laparoscopic surgery, a video camera shows the surgeon via a monitor the location of the cyst. Using thin instruments inserted through small incisions, the surgeon removes the cyst. Done either under anesthesia or standing, a laparoscopic surgery can be used only on smaller cysts or tumors. Because the incision is so much smaller than with standard surgery, a mare recovers much faster. Within two weeks post-surgery, she can usually get back into some light work.
- Western Veterinary Conference: Reproductive Surgery in the Mare – Indications and Surgical Procedure
- Equine Veterinary Centre: Our Equipment
- Journal of Equine Veterinary Science: Ovarian Fibrothecoma in Mare – Case Report
- Vetstream: Ovary -- Colpotomy
- International Veterinary Information Service: Review of Ovarian Abnormalities in the Mare
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