Ovarian Remnant Syndrome in Pets: What You Need to Know

Ovarian Remnant Syndrome (ORS) is a rare but significant condition that can affect pets, particularly female cats and dogs that have undergone spaying (ovariohysterectomy). This condition occurs when a small piece of ovarian tissue is left behind during the spaying procedure, allowing the pet to continue experiencing heat cycles and associated symptoms despite being “spayed.”

In this article, we’ll explore what ovarian remnant syndrome is, how it occurs, the symptoms to watch for, and the treatment options available for affected pets.

What is Ovarian Remnant Syndrome?

Ovarian Remnant Syndrome occurs when a small portion of the ovary is not completely removed during spaying surgery. This leftover ovarian tissue can become reactivated over time, releasing hormones that cause the pet to continue going into heat, even though the uterus has been removed.

Spaying is intended to stop the reproductive cycle in female pets, so when ORS occurs, it can be confusing and concerning for pet owners. Although spaying typically prevents the production of estrogen and progesterone, which control a pet’s reproductive cycle, any remnant ovarian tissue can still produce these hormones.

How Does Ovarian Remnant Syndrome Happen?

ORS can occur for several reasons, most commonly due to technical challenges during surgery:

1. Inadvertent Retention of Ovarian Tissue: During spaying, the ovaries must be Fully excised. However, in some cases, small pieces of ovarian tissue may be accidentally left behind, either because the tissue was hard to reach or because of difficulty identifying all of it.
2. Ectopic Ovarian Tissue: Some animals are born with small amounts of ovarian tissue in abnormal locations within their abdomen. This tissue might be missed during surgery, leading to continued hormone production.
3. Re-growth of Ovarian Tissue: In rare cases, small pieces of ovarian tissue that remain can regenerate over time, leading to resumed hormonal activity.

Symptoms of Ovarian Remnant Syndrome in Pets

The primary symptom of ORS is the recurrence of estrus, or heat cycles, in a female dog or cat that has already been spayed. Typical signs include:

• Swollen Vulva: Pets with ORS may display a swollen or enlarged vulva, which is usually a sign of being in heat.
• Behavioral Changes: Just as they would during a regular heat cycle, pets may show increased affection, restlessness, or vocalization.
• Attraction to Male Pets: Female pets with ORS may attract the attention of male dogs or cats, as they can release hormones that signal they are in heat.
• Vaginal Discharge: A small amount of bloody or clear discharge may be seen, which is a sign of hormonal activity.

It’s important to note that ORS can appear weeks, months, or even years after a spay surgery, making it difficult for some pet owners to recognize that these symptoms are linked to incomplete removal of ovarian tissue.

Diagnosing Ovarian Remnant Syndrome

If your pet starts showing signs of being in heat after being spayed, it’s essential to consult a veterinarian. Diagnosing ORS involves several steps:

1. History and Physical Exam: The Vet will ask for the pet’s medical history, particularly focusing on the spay procedure. They may also perform a Physical examination to look for signs of heat.
2. Hormonal Testing: Blood tests to measure hormone levels, particularly estrogen or progesterone, can help determine whether your pet is still producing reproductive hormones. A progesterone test is often done 1-2 weeks after the symptoms of heat are noticed.
3. Vaginal Cytology: This involves examining cells from the pet’s vaginal wall under a microscope. In animals experiencing estrus, these cells change in a recognizable way due to hormonal influence.
4. Ultrasound: In some cases, an ultrasound may be used to locate any remaining ovarian tissue in the pet’s abdomen.
5. Hormone Stimulation Tests: Veterinarians might also perform a GnRH (gonadotropin-releasing hormone) stimulation test to confirm the presence of functional ovarian tissue.

Treatment Options for Ovarian Remnant Syndrome

The only effective treatment for ovarian remnant syndrome is surgery to remove the remaining ovarian tissue. This is called an ovarian remnant removal surgery. The procedure requires careful exploration of the abdomen to locate and excise any remnants of ovarian tissue.

Because ovarian remnants can be difficult to detect, this surgery is often more complex than the initial spaying procedure. However, once the remaining tissue is Fully removed, the pet will no longer experience heat cycles.

After surgery, the Vet will typically monitor hormone levels to ensure that the remaining tissue has been completely removed.

Complications and Risks of ORS

If left untreated, ORS can lead to complications. The ongoing hormone production can cause:

• Pyometra: While a spayed dog or cat doesn’t have a uterus, persistent hormone production can lead to pyometra, an infection of any remaining reproductive tissue, which is a life-threatening condition.
• Increased Cancer Risk: Prolonged exposure to estrogen can increase the risk of certain cancers in female dogs and cats.
• Behavioral Issues: Recurring heat cycles can cause behavioral changes such as aggression or anxiety in some pets.

Preventing Ovarian Remnant Syndrome

ORS is largely a surgical complication, so the most important way to prevent it is to ensure that the initial spaying procedure is done by an experienced and skilled veterinarian. While it’s a rare occurrence, discussing the risks with your Vet before surgery and ensuring a thorough spay procedure can help reduce the likelihood of ORS.

Conclusion

Ovarian Remnant Syndrome is a rare but serious condition in spayed female dogs and cats that can cause them to continue experiencing heat cycles. It is caused by leftover ovarian tissue that was not completely removed during the spay surgery. While the symptoms can be troubling, the condition is treatable through additional surgery.

If you suspect your pet might have ORS, it’s important to seek veterinary advice. Early diagnosis and treatment can help prevent further complications and ensure your pet’s long-term health and well-being.