Intact (i.e., unspayed) female pets are at an increased risk for certain cancers and a serious uterine infection called pyometra. Pyometra is common in older intact females (i.e., those who have undergone multiple heat cycles throughout their lives) and can quickly become a life-threatening situation. The West Vets ER team wants pet owners to understand the serious nature of pyometra, learn to recognize the signs, and use the following information to make informed decisions about whether or when to spay their pets.

Aging female pets: A recipe for pyometra

Pyometra is a serious uterine infection that typically develops in older dogs and cats. Normally, the body fights bacteria that enter the sterile uterus from the unsterile vagina, effectively preventing infections. However, hormones released during the heat cycle trigger the thickening of the uterine lining in preparation for pregnancy, and bacteria that enter during this time are more likely to survive in the now-hospitable uterus. As pets get older, their hormones can induce cystic changes in the uterine lining that further feed bacteria and increase their pyometra risk. 

Once established inside the uterus, the bacteria have plenty of nourishment and proliferate rapidly. The uterus becomes large and distended with pus and debris, and bacteria and toxins can leak into the bloodstream or abdomen. This infection spreading through the bloodstream (i.e., sepsis) makes pyometra life-threatening.

How to spot pyometra signs in your pet

Pyometra signs are often vague—the hallmark sign is a bloody or purulent (i.e., containing pus) vaginal discharge, but this is not present in all cases, because the cervix, which separates the vagina and uterus, can be open or closed. Fastidious cats may also clean away their discharge. Your pet may appear generally unwell, with signs that include:

Pyometra most often occurs in older, intact females a month or two after they finish a heat cycle, but any age pet can be affected.

How veterinarians diagnose pyometra in pets

Our veterinary team performs a complete physical examination on all sick pets and will collect their history from the pet owner to determine the most likely causes for their presenting signs. Then, our team may order the following tests to confirm or rule out a pyometra diagnosis and evaluate the pet’s overall health status:

  • Blood and urine tests
  • X-rays
  • Ultrasound
  • Vaginal cytology

How veterinarians treat pyometra in pets

The ideal pyometra treatment is surgical removal of the infected uterus and the ovaries, which produce the reproductive hormones that create an environment favorable for infection. The surgery is delicate, because the veterinarian must carefully remove the fragile, pus-filled organ without spreading the infection and remove all traces of ovarian tissue to prevent infection recurring in the small tissue stump left behind. Most pets must spend several days in the hospital before and after surgery to stabilize their condition and receive strong intravenous antibiotics.

A non-surgical pyometra treatment is available for valuable breeding pets but is generally not recommended. The treatment, which involves injections to induce uterine contractions to expel the infected contents, combined with oral or injectable antibiotics, is risky, because the uterus could rupture during contractions and lead to life-threatening sepsis. If treatment is successful, the pyometra is likely to return in the future.

To spay or not to spay: Preventing pyometra in pets

Spay surgery (i.e. ovariohysterectomy) removes a dog’s or cat’s ovaries and uterus to prevent the pet from reproducing. The surgery not only prevents unwanted pregnancies, but also reduces cancer risks, behavioral issues, and pyometra risks. Unless pets are slated for a breeding program, most females should be spayed at a young age. The exact timing depends on their breed and health status, which you should discuss with your primary veterinarian. 

Many pet owners who chose not to spay their pet when they were young think their older pet will no longer benefit from surgery. Although a late-in-life spay won’t reduce mammary cancer risks, the procedure can still ward off pyometra, uterine cancer, or ovarian cancer and is worthwhile for retired breeding animals or other pets.

Pyometra can mimic many other illnesses, but you should suspect pyometra and treat the issue as an emergency any time an older, intact female shows compatible signs. Contact the West Vets ER team if your pet needs urgent or emergency care, or to discuss your pet’s signs and symptoms with a knowledgeable team member.