Hormonal changes in a female pet’s reproductive tract can lead to a serious infection called pyometra that, if not treated promptly, is a life-threatening condition for your pet. Our Family Veterinary Care of Oakdale team wants to help prevent an emergency situation, and we offer information about pyometra and explain how you can safeguard your four-legged friend.

Pet pyometra basics

When a female pet is ready to mate, they go into estrus (i.e. heat), which means hormonal changes make their body more receptive to pregnancy. Several factors related to this process contribute to pyometra, including:

  • Cystic endometrial hyperplasia — For several weeks after estrus, progesterone levels remain elevated, preparing the uterus for pregnancy by thickening the uterine wall. If your pet doesn’t get pregnant, their uterine lining continues to thicken after each estrus cycle, which can lead to cyst formation in the uterine wall (i.e., cystic endometrial hyperplasia). The cysts secrete fluid that creates an ideal environment inside the uterus for bacterial growth.
  • Elevated progesterone levels — Elevated progesterone levels inhibit the uterine wall’s ability to contract and expel fluid and bacteria.
  • Relaxed cervix — Usually the female pet’s cervix is tightly closed, but during estrus, the cervix relaxes to allow sperm to enter. This also allows bacteria to ascend from the vaginal area.
  • White blood cell (WBC) inhibition — During estrus, WBCs that normally fight infection are prevented from entering the uterus to protect the sperm, which allows bacteria to multiply and grow in the uterus.

Pet pyometra signs

Pyometra can occur in any female pet who has not been spayed, but is most commonly seen in middle-aged and older pets who have never been pregnant. Pyometra typically occurs two to eight weeks after the pet’s last estrus cycle, and is classified as closed or open:

  • Open pyometra — Open pyometra means the cervix remains open, which allows purulent material (i.e., pus) to drain from the uterus through the vagina. In these cases, the only sign may be vaginal discharge, which you may notice on your pet’s hair under their tail or on their bedding. Cats are meticulous groomers, and often don’t leave behind evidence of vaginal discharge. Other signs may include lethargy, fever, decreased appetite, and increased thirst and urination.
  • Closed pyometra — Closed pyometra means the cervix is closed, trapping the infection in the uterus. These pets tend to be much more seriously ill than pets with open pyometra, because the trapped bacteria release toxins. Signs include lethargy, fever, inappetence, vomiting, diarrhea, and increased thirst and urination. 

Pyometra should be suspected in any sick female pet who has not been spayed.

Pet pyometra diagnosis

Diagnostics to identify the condition include:

  • History — We ask questions about your pet’s spay status and the dates of their last estrus.
  • Physical examination — We perform a thorough physical examination looking for abnormalities, such as vaginal discharge or a distended, painful abdomen.
  • Blood work — We perform a complete blood count (CBC) and biochemistry profile to obtain information about your pet’s overall health and to determine if their WBC count is elevated, which typically occurs during pyometra.
  • Urinalysis — Pyometra typically hinders the kidney’s ability to concentrate urine, and a urinalysis helps us determine if your pet’s urine is too dilute.
  • Imaging — Imaging techniques, including X-rays and ultrasound, are especially helpful to make a closed pyometra diagnosis.
  • Vaginal culture — We may perform a vaginal culture to determine the causative pathogen.

Pet pyometra treatment

Treatment options for pyometra include:

  • Surgery — By far the most recommended pyometra treatment  is surgical removal of the uterus and ovaries. However, spaying a pet with pyometra, unlike a simple typical spay, can be challenging, because the pet most often is extremely sick, the surgeons must ensure the uterine contents don’t spill into the pet’s abdominal cavity, and the pet may bleed excessively. But, once the pet’s infected uterus is removed, they usually recover quickly.
  • Prostaglandins — For pets who are highly valued as breeding animals, prostaglandin therapy is a potential option, although this treatment has some serious disadvantages:
    • Pets don’t clinically improve for at least 48 hours, and the treatment is not suitable for severely ill pets who need immediate intervention.
    • The treatment leads to side effects such as restlessness, vomiting, diarrhea, and abdominal pain.
    • Prostaglandins cause the uterus to contract and can lead to uterine rupture, a severe condition that can be life-threatening.
    • Breeding must occur on the next estrus cycle to prevent pyometra recurrence.

Pets who experience pyometra are at higher recurrence risk, and a pet who undergoes prostaglandin treatment to preserve their breeding ability should be spayed as soon as their breeding purposes are finished.

Pet pyometra prevention

You can easily protect your pet from pyometra by having them spayed when they are young. However, hormones play an essential role in your pet’s development, and we don’t recommend spaying your pet too early. For cats, we recommend waiting until they are 6 months of age. For dogs, our recommendation is based on their breed, lifestyle, and disease risk, but we usually like to spay them between 9 and 12 months of age. 

Contact our Family Veterinary Care of Oakdale team, so we can determine the best time to spay your female pet and protect them against pyometra.