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Pyometra in Female Dogs: One More Reason to Consider Spaying and Neutering

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Bitches that are not spayed are at high risk of developing reproductive pathologies such as pyometra. Find out what this disease is and why it compromises your pet's life.
Pyometra in Female Dogs: One More Reason to Consider Spaying and Neutering
Last update: 08 July, 2023

Pyometra is one of the most common reproductive diseases in female dogs. In fact, an article in the journal Reproduction in Domestic Animals states that about 20% of all female dogs that aren’t spayed suffer from it before the age of 10 years.

Because of the serious complications it creates in animal health, pyometra in female dogs is considered an emergency. For this reason, it should be treated as soon as possible.

Throughout this article, we’ll detail key aspects of the disease such as causes, types of pyometra, symptoms, as well as the best way to treat and prevent it. If you want to learn more about this relevant canine pathology, don’t hesitate to continue reading the following content.

What is pyometra and what are its types?

Pyometra is the inflammation and accumulation of purulent material inside the uterus, due to a bacterial infection. Although it can occur in females of any breed or age, a publication of the Brazilian Journal of Veterinary Pathology reveals that female dogs between 6 and 10 years of age, as well as the following breeds, are more predisposed to suffer from it:

Likewise, as the authors mention, two types of pyometra can occur in female dogs:

  • Open cervix pyometra: In these cases, purulent exudate drains through the cervix. As a result, a bloody vulvar discharge is observed, accompanied by pus and a very bad odor.
  • Closed cervix pyometra: On the contrary, the cervix is closed and the purulent exudate is retained inside the uterus. It’s considered the most serious type, as there’s a risk of developing septicemia. This condition can lead to the death of the animal, since it’s a generalized infection of the whole body.
Unlike the previous one, closed cervix pyometra is more difficult to identify, because there’s little or no vaginal discharge.

What are the causes of pyometra in female dogs?

Although the pathogenesis of pyometra isn’t entirely clear, an article in the journal The Veterinary Clinics of North America states that its causes include both hormonal and bacterial factors.

On the one hand, after estrus – a period known as the luteal phase or diestrous – progesterone generates certain alterations in the reproductive system of bitches. These include the following:

  • Growth and proliferation of endometrial glands
  • Increase of intrauterine secretions
  • Closure of the cervix
  • Suppression of myometrial contractions

Although these changes occur naturally to favor the growth of the fetus in pregnant dogs, the uterus – of those that aren’t pregnant – is exposed to the colonization of opportunistic bacteria and their accumulation inside.

In addition, during the luteal phase, the local defense cell response decreases, and the resistance of the uterus to bacterial infections decreases.

On the other hand, according to a review reported in The Indian Journal of Veterinary Sciences and Biotechnology, among the microorganisms implicated in pyometra in bitches can be found:

  • Escherichia coli
  • Klebsiella spp
  • Streptococcus spp
  • Staphylococcus spp
  • Pseudomonas spp

These bacteria usually move up from the vagina into the uterus, and proliferate if ideal conditions for their growth are present.

Among other things, treatments to prevent estrus and pregnancy with steroid hormones, such as progesterone and synthetic estrogens, increase the risk of developing the disease. In addition, reproductive pathologies such as cystic endometrial hyperplasia increase the susceptibility of the uterus to infection. So states an article in the journal Theriogenology.

Some figure
Escherichia coli is the main bacterium associated with cases of pyometra in female dogs. Credit: Eric Erbe/Wikimedia Commons.

What are the symptoms?

As evidenced in previous lines, the development of the disease occurs during the luteal phase, so symptoms usually appear between 3 to 5 weeks after estrus. Among the most common signs are the following:

  • Inappetence
  • Depression
  • Fever
  • Anorexia
  • Increased urination
  • Increased water consumption
  • Diarrhea
  • Vomiting
  • Dehydration
  • Distended abdomen (closed pyometra)
  • Purulent and bloody vaginal discharge (open pyometra)

Why is it considered a life-threatening disease?

According to the description of a study in the journal BMC Veterinary Research, one of the most serious complications of pyometra in female dogs is sepsis. This condition – which can be fatal if not treated in time – occurs when toxins produced by the bacteria spread throughout the body, through the bloodstream.

This, in turn, generates what is known as systemic inflammatory response syndrome (SIRS), which leads to alterations in different body systems and the failure of organs such as the heart, kidney, or liver. It tends to occur more frequently in female dogs with closed pyometra.

Another life-threatening complication is peritonitis. This occurs when the accumulation of purulent material is so great that the uterus is perforated. Therefore, the pus passes into the abdominal cavity and causes inflammation of the peritoneum.


When the above-mentioned symptoms appear, you will need to consult a veterinarian. In essence, after the study of the clinical history and examination of the patient, they will recommend the following tests:

  • Radiology
  • Ultrasound
  • Vaginal cytology
  • Complete blood analysis
  • Urinalysis

How is pyometra in female dogs treated?

The treatment of choice for both open and closed pyometra is surgical intervention. The procedure performed is ovariohysterectomy (OVH) or spaying, which involves complete removal of the uterus and ovaries.

However, the patient must first be stabilized with adequate intravenous fluid therapy. The purposes of this measure are distinguished as follows:

  • To restore blood pressure
  • To correct dehydration
  • To restore electrolyte balance
  • To prevent organ failure and possible shock or clotting problems.
In addition, antibacterial drugs such as ampicillin should be started immediately.

Although questionable, some studies suggest possible drug-based treatment of pyometra. For example, a publication in the journal Reproduction in Domestic Animals, describes the following protocol:

  • Fluid therapy to resolve dehydration
  • Antibiotics such as amoxicillin + clavulanic acid for infection
  • Antiprogestagens such as aglepristone to reduce the effect of progesterone in the body
  • Prostaglandins to increase the contraction of the uterine musculature and favor the expulsion of purulent material

However, it’s important to emphasize that this type of management should only be performed in cases of open pyometra. It isn’t recommended in cases of closed cervix, due to the risk of rupture of the uterus and possible peritonitis. And much less so in sepsis or when other organs are compromised.

Some figure
Female dogs with pyometra should undergo stabilization treatment before surgery. Credit: Shutterstock.

What is the prognosis?

Generally, the survival rate for bitches undergoing timely surgical treatment is high. In fact, a study reported in the Journal of The American Veterinary Medical Association reported a 97% survival rate in bitches with pyometra undergoing OVH.

However, when the disease is allowed to progress, the prognosis worsens. Factors influencing poor prognosis include the following:

  • High blood BUN (urea nitrogen) and creatine concentrations, which are indicative of renal failure
  • Heart murmurs
  • Leukopenia (low levels of defense cells in the blood)
  • Systemic inflammatory response syndrome (SIRS)
  • Peritonitis

Spaying: the best method of preventing pyometra in bitches

As you could see, all the problems associated with pyometra in bitches are solved by spaying. Thanks to this procedure, the bitch will no longer have a uterus and ovaries, so there will be no way for her to have the disease. In addition, the risk of suffering from other pathologies such as mammary tumors will be reduced.

In addition, it’s recommended to avoid the administration of hormonal contraceptives, as well as to follow up the bitch’s estrus. Likewise, it’s advisable to perform periodic ultrasound monitoring.

Now that you know everything about this serious pathology, it’s your responsibility to determine whether the reproductive capacity of your pet is more valuable than her health and well-being.

Finally, remember to always be alert to behavioral changes that could point to a possible case of pyometra. Don’t forget that, in some cases, the disease progresses silently until it may be too late.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.