In the United States, most female dogs and cats who aren’t slated for breeding are spayed. Removing their uterus and ovaries prevents unwanted pregnancies and eliminates the potential for reproductive and mammary cancers. Pets who are not spayed at a young age are at risk for a serious, often life-threatening uterine infection called pyometra. 

The Creature Comforts Veterinary Service team wants pet owners and breeders to understand how pyometra develops and how to identify the problem. The sooner the infection is diagnosed, the better the potential outcome. Here is our guide to pyometra in female pets.

How pyometra develops in pets

Pyometra can develop in pets whose reproductive system is intact. The condition’s etiology is multifactorial—meaning more than one condition must occur at once to create the perfect storm. First, the pet’s reproductive hormones and natural estrus cycle lead to the uterine lining thickening, and the cervix (i.e., the opening between the uterus and vagina) opens. Next, bacteria can ascend from the vagina into the uterus, where they flourish in the thickened lining. These harmful bacteria may come from a concurrent bladder infection or fecal material contaminating the vaginal environment. The infection quickly proliferates and the uterus fills with pus, which may or may not leak out from the cervix.

Pets at risk for pyometra development

All intact female pets are at risk, including young puppies, although the risk is greatest in older dogs and cats who have undergone multiple heat cycles. The risk may be higher in intact pets who have never been pregnant or given birth, or in pets who develop cysts in the uterine lining. Pyometra tends to develop one to two months after a heat cycle ends. Rarely, spayed pets develop the infection in the small tissue left behind after surgery—in this case, the condition is called uterine stump pyometra.

Pet pyometra signs

Once the uterus becomes distended with pus, contents can leak into the abdominal cavity and the bloodstream. Toxins and bacteria quickly lead to shock, multiple organ failure, or death without rapid intervention. Pets with a closed cervix who have no vaginal discharge are sicker than those with an open cervix, which allows some of the pus to drain outside the body rather than leaking into the abdomen. Pyometra signs can mimic many other illnesses, but may include the following:

  • Bloody or thick vaginal discharge—this is not present if the cervix is closed
  • Fever
  • Lethargy
  • Vomiting
  • Increased thirst and urination
  • Decreased appetite

What to do if your pet shows pyometra signs

Pyometra is a veterinary medical emergency. If your female pet becomes sick with no other explanation, you should assume a pyometra and seek immediate veterinary attention. Our hospital is open 24/7 for emergencies—simply call ahead to let us know about your pet’s impending arrival, so we can prepare to meet their needs efficiently.

Pet pyometra diagnosis and treatment

Veterinarians are trained to suspect pyometra in any sick, intact female pet. Diagnosis is relatively straightforward in open-cervix cases but can be more difficult to confirm in closed-cervix cases. Our team may order the following tests to fully evaluate your pet’s overall condition and confirm the pyometra diagnosis:

  • Complete blood count and blood chemistry profile
  • Urinalysis
  • Abdominal X-ray
  • Abdominal ultrasound
  • Vaginal cytology

The pyometra treatment of choice is emergency surgery to remove the uterus and ovaries, which is similar to a routine spay procedure, but significantly more delicate, because the surgeon must avoid rupturing the delicate uterine tissue and further spreading the infection. Some pets with pyometra are quite sick and must be stabilized as an inpatient before undergoing surgery and then must remain hospitalized for several days. Fluids and antibiotics are necessary before and after the surgery. 

An alternative medical treatment protocol exists that attempts to preserve the reproductive ability of valuable breeder pets, but this treatment is risky and doesn’t always work. Only carefully selected candidates may undergo medical therapy.

Pet pyometra prevention

The best prevention for pyometra is to spay your female pet when young—the ideal timing will depend on their species and expected adult size. Breeding animals should be spayed as soon as their reproductive career ends to reduce pyometra risk in their later years.

Any pet—especially an intact female—who develops generalized illness signs or vaginal discharge should be examined as soon as possible by one of our Creature Comforts Veterinary Service team members. Call us anytime, day or night, if you have concerns about your pet’s condition or believe your pet needs urgent veterinary care. Our care team handles a full range of routine and sick pet care during regularly scheduled daytime appointments, as well as emergencies.