Pet insurance companies call it a pre-existing condition. I call it pyometra.

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Dog Insurance

Canine Pyometra

Pyometra is a bacterial infection of the uterus. The uterine lining gets thick, and then infected by bacteria and filled with pus. Bacteria from the uterus can leak into the blood and abdomen, causing shock and death.

Pyometra is a life-threatening condition that requires quick and aggressive treatment.

Pyometra most commonly occurs in older, non-spayed, females following a heat cycle.


With every heat cycle, the uterine walls thicken, preparing for pregnancy. If pregnancy does not occur after a few cycles, the following will cause infection:

  • Cysts: will form in the thickening lining and produce fluids, a perfect environment for bacteria to grow
  • Bacteria: enter the uterus from the vagina
  • Thick uterine walls: prevent the uterus' muscles from squeezing together to push out the fluids and bacteria

During a heat cycle, white blood cells cannot enter the uterus. Therefore, when the bacteria grow, there is nothing to stop it.

Another cause can be reproductive medications that may contain hormones that cause the uterine wall to thicken. If your dog is not spayed, and is on reproductive medicine, your veterinarian should monitor her.


Signs depend if her cervix (the opening to the uterus) is open or closed.

Open cervix:
Foul-smelling vaginal discharge (blood, pus or mucus) is the first sign of an infected uterus. You may see this discharge on your pet's skin, on the hair below the tail, or anywhere she has lain. These dogs seem less sick because the infection is able to leave the body.

Keep in mind: many dogs clean themselves of vaginal discharge before the owner sees it.

Closed cervix:
There will be no vaginal discharge. Rather, the infection leaks into the bloodstream and abdomen, leading to shock and death. These dogs will be sicker than those with an open cervix because the infection stays in their body.

Common signs with a closed cervix:

  • Lethargy and depression
  • Loss of appetite
  • Excessive drinking and urinating
  • Vomiting
  • Abdominal pain and swelling
  • Continuous grooming at the vaginal opening

If you do not have your dog spayed, and she displays any of the above signs, go to your veterinarian right away. Pyometra is fatal without immediate treatment.


To diagnose your dog with pyometra, your veterinarian may perform the following:

  • Blood tests: dogs with pyometra usually have a very high amount of white blood cells
  • Urinalysis: dogs with pyometra have a low urine concentration
  • Culture analysis: study a sample of the vaginal discharge under a microscope
  • Radiographs (in a case of a closed cervix): will show a swollen uterus with thick walls containing fluid
  • Ultrasound (in a case of a closed cervix): will differentiate between a swollen uterus and pregnancy


Pyometra is life threatening, and needs aggressive treatment. The best treatment is an emergency spaying surgery, which is complicated because the infected contents of the uterus can spill.

The emergency spaying surgery includes:

  • Complete removal of the ovaries to prevent future heat cycles and a recurrence of pyometra
  • Hospitalization for a few days after the surgery
  • IV fluids to stabilize the dog before and after surgery
  • Antibiotics after surgery for any remaining infection

With an open cervix, and if the owner insists on preserving the animal's reproductive capability, your veterinarian may try treating the pyometra with hormone injections. These cause the uterus to contract and expel the pus.

This treatment is dangerous because the contracting uterus can rip and spill puss. Its success rate is lower and leaves room for a relapse. Also, your dog will not improve for about forty-eight hours, so it is not an option for severely ill dogs.

Side effects last for a few hours after each injection, and become milder with each treatment:

  • Abdominal pain from the cramping
  • Restlessness
  • Panting
  • Salivation
  • Vomiting
  • Defecation


Spaying your dog is a simple way to prevent pyometra. Otherwise, they will eventually contract pyometra.

The importance of spaying cannot be stressed enough. A dog will benefit from spaying at any age, but it's best to have them spayed at the youngest age possible


Most dogs will recover successfully with immediate surgery. However, if treatment is not performed promptly, pyometra is fatal because of the toxic effects of the pus.

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