What Is Pyometra in Dogs?

Medically Reviewed by Amy Flowers, DVM on December 11, 2021
3 min read

Pyometra is the infection in the uterus (womb) of a female dog. It is caused by hormonal changes in the body that fill the uterus with pus. Pyometra is a life-threatening condition that requires immediate medical attention. Here are the common causes, symptoms, and treatments of pyometra in dogs.

Unneutered dogs that still have reproductive organs are more likely to get pyometra, especially when they are over age 6. 

The chances of developing pyometra are higher when your unneutered dog is out of heat. During this time, the dog goes through hormonal changes. When the heat period is over, most dogs return to normal. But, some may develop an infection or pyometra in their uterus.

As the infection grows, the uterus gets filled with pus. If not treated on time, the pus can cause blood poisoning, peritonitis, kidney failure, or even death.

Pyometra can be 'open' or 'closed.' In an open pyometra, the uterus’ entry remains open, and you can see pus or blood coming out of your dog's vulva. 

In closed pyometra, the uterus is shut, and you can't see the discharge. This condition is more dangerous as the uterus can burst.

In rare cases, a dog may also develop a particular type of pyometra called a stump pyometra. It happens when a small uterus stump remains inside the dog and gets infected.

The primary cause of pyometra in dogs is hormonal change during each heat cycle. The cycle changes the uterus and makes it thicker with tissues to support pregnancy. When these changes keep happening, the uterus can change permanently and have excess tissue.

The transformation of the uterus makes it more vulnerable to infection. It also weakens the uterus' ability to fight off any infectious bacteria.

Pyometra commonly happens due to the E. coli bacterium, mostly a few weeks after the female dog completes the heat period. 

Progesterone-based drugs can also cause pyometra due to the changes they make in the uterus. Dogs already taking hormone therapy for treating conditions of the reproductive system must be monitored for pyometra. 

The symptoms of pyometra in dogs usually start after four to eight weeks of a heat period. The common ones include:

  • An increased urge for water 
  • Nausea or vomiting
  • A discharge from the vulva (pus)
  • Bloated tummy
  • Frequent panting 
  • Fatigue
  • Appetite changes
  • Increased urination
  • Unusual collapse

These signs can be the indication of other underlying medical conditions, as well. Keep an eye on your pet and seek medical attention as soon as you observe any change in their behavior.

The vet will start the diagnosis of your dog's condition with questions about the heat cycle. You will need to tell the doctor about your dog's changing behavior and if she has been cleaning herself more around the vulva.

The vet may first check any swelling in your dog's abdomen with radiographs or an ultrasound exam.

The initial stage of pyometra usually comes with a slight vaginal discharge with no prominent symptoms. Pets diagnosed with pyometra later show visible signs.

Dogs with pyometra also have an increased white blood cell count and globulins in the blood. Some dogs may also have painful, enlarged abdomen.

The preferred pyometra in dogs treatment is surgery. The vet surgeon usually performs an ovariohysterectomy (spay) to remove the infected uterus and ovaries. This surgery is more complicated than routine spay.

Dogs diagnosed in the early stages of their illness are considered good candidates for a successful surgery. The risks of complications and extended hospitalization are higher as the pyometra develops.

After the surgery, typically, intravenous fluids (IV) are needed.

Pyometra is a medical emergency that needs immediate treatment. If you notice symptoms or changes in your dog's behavior, call your vet. Early diagnosis lowers the risks of complications.