Ovarian Remnant Syndrome in Dogs

Key takeaways

Ovarian remnant syndrome occurs uncommonly in female dogs when part of the ovarian tissue remains in the body after an ovariohysterectomy (spay).

  • This condition leads to the continued production of hormones and signs typical of heat (estrus)
  • Intact female dogs go into heat every 6 to 8 months and the classical signs are the attraction of male dogs, bloody vaginal discharge, swelling of the vulva, and excessive licking of the genital area
  • Ovarian remnant syndrome is diagnosed through blood work that evaluates the level of hormones in the bloodstream
  • Vaginal cytology and abdominal ultrasound are also often necessary for diagnosis
  • Typical treatment consists of surgical removal of all residual ovarian tissue
  • If the residual tissue can be found, surgery is usually effective and without complications
  • It is not always possible to find the residual ovarian tissue, and in this case, referral to a specialist may be suggested
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A closer look: Ovarian Remnant Syndrome in Dogs

The ovaries are part of the female reproductive system. Part of their function is secreting sex hormones involved in regulating reproduction and heat (estrus) cycles. During most sexual alteration (spay) surgeries, the ovaries and uterus are completely removed. With the removal of ovaries, the secretion of sex hormones is expected to cease, which stops heat cycles from continuing. In some cases, spayed dogs may continue to have symptoms of estrus, which suggests active ovarian tissue is still present in the body.

Depending on hormone levels at the time of spay surgery, some female dogs might still present signs of heat for a while after the surgery but do not have ovarian remnant syndrome. Circulating hormones in the bloodstream take time to wear off, so some signs of heat after spay do not suggest ovarian remnant syndrome unless they persist.

Ovarian remnant syndrome is an uncommon condition and is a possible complication of spaying. In most cases the symptoms are not worrisome, but complications can arise from the continued presence of hormones. These include ovarian tumors, mammary-gland tumors, and stump pyometra, a serious and possibly life-threatening condition. Ovarian remnant syndrome can usually be solved surgically, but it is not always easy to find the residual tissue.

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Risk factors

Left untreated, the persistent production of hormones by ovarian remnants can lead to serious complications, including stump pyometra (a potentially life-threatening infection of the part of the uterus that remains after spaying) and increased risk of mammary-gland and ovarian tumors.

Affected dogs may also show signs of false pregnancy, such as swollen mammary glands and behavioral changes.

All female dogs undergoing spay surgery are at some risk of ovarian remnant syndrome. It is important to note the risk of ovarian remnant syndrome does not outweigh the benefits of sexual alteration surgery, as the condition is rare.

Possible causes

Ovarian remnant syndrome is caused by ovarian tissue that is unintentionally left behind after spaying. This retained ovarian tissue develops a blood supply and hormone secretion resumes. Retention of ovarian tissue is a possible complication of any spay surgery and can occur regardless of the skill or experience of the surgeon.

Main symptoms

Symptoms of ovarian remnant syndrome are the same as those seen during the normal canine estrus (heat), and repeat every six to eight months.

Testing and diagnosis

The diagnostic process consists of blood work to evaluate hormone levels in the bloodstream. Sometimes, abdominal ultrasound can show if remaining ovarian tissue is present in the body. Vaginal cytology is often necessary to look for a specific type of cell that indicates the presence of sex hormones.

Steps to Recovery

The condition lasts until the hormone-secreting ovarian tissue is surgically removed. If the residual tissue is found, the surgery is usually effective, and the prognosis is excellent. However, it is not always possible to find the residual tissue, and in this case, referral to a specialist is suggested. Medications to suppress ovarian activity are also available, but are usually not recommended due to side effects.


Ovarian remnant syndrome is a possible complication of spay surgery with no specific preventive measures.

Is Ovarian Remnant Syndrome in Dogs common?

Ovarian remnant syndrome is an uncommon complication of ovariohysterectomy surgery.

Typical Treatment

Surgical removal of retained ovarian tissue

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