Pyometra in Dogs: Find Out How To Prevent This Deadly Condition

By Chelsea Hunt-Rivera / March 26, 2018

Making crucial decisions for your dog’s well-being can often be accompanied by uncertainties and anxiety as to what choice is the right choice. Many times, people will tell us what we should do, but not why. “Everyone does ____, _____, and ____, so you should, too.” You can fill in the blanks. We have all faced these particularly uncertain situations that don’t only affect us, but our four-legged friends. One of the scariest, uncertain situations we can find our pups in is Pyometra.

What is Pyometra in Dogs?

pyometra in dogs visual

Pyometra is an infection of the uterus that is not only serious but often life-threatening and requires a pet owner to know what signs to look for and to act fast.

Pyometra, in Greek, translates to ‘pyo’ meaning pus, and ‘metritis’ meaning uterine inflammation.

The Basics

Most commonly, Pyometra is seen in female dogs over the age of six who are not spayed and have not been pregnant. The female usually starts showing signs of the disease two to four months after a heat cycle.

It primarily occurs when bacteria enter the uterus in the dog’s estrus (heat) cycle. Hormonal regulation of the uterus allows an infection to start.

Dogs that have heat cycles not resulting in egg fertilization have a thickening of the uterus walls which makes passing excess fluids impossible.

The toxicity of the uterus is an infection known as Pyometra.

Now, let’s dive into the details. Staying informed and alert is massively important when it comes to your pup’s health.

What is a Uterus

canine uterus

The uterus is commonly referred to as the ‘womb’ in female mammals. It is a hollow organ that is responsible for the evolution of the embryo and fetus during reproduction.

What is a Uterine Infection

Up until recently, Pyometra was thought to solely be a uterine infection, or simply a virus in the uterus. While Pyometra falls under the category of being a ‘uterine infection,’ scientists have recently discovered that it is much more than a mere infection.

Modern science shows that Pyometria differs in that it’s a hormonal abnormality that can develop with or without an existing secondary bacterial infection. This new development also increases the severity of Pyometra, having cases where the dog passes away due to complications of the disease.

Uterine Infections Other Than Pyometra

Other uterine infections exist that are not considered to be Pyometra. In general terms, a uterine infection is the result of inflammation of the uterus due to bacterial contamination.

Usually, a uterine infection that is not classified as Pyometra occurs within a week of a dog giving birth. It can also happen with bacteria entering the body after non-sterile artificial insemination, as well as a natural or medical abortion. Commonly, the dog’s weakened immune system is unable to combat such volumes of bacteria which leads to a blood infection.

Progesterone-Based Drugs

The use of progesterone-based drugs can cause changes in the uterus. Furthermore, the use of estrogen-based drugs will cause progesterone to have strong effects on the uterus. These drugs are typically used to treat reproductive system conditions. Any dog receiving the hormones should be closely watched as Pyometra can form.

While different from Pyometra, an untreated infection in the uterine wall can still result in sterility and even death. Any and all viruses should be diagnosed and treated as soon as symptoms develop.

Pyometra is a uterine infection, but a uterine infection isn’t always Pyometra. However, both viruses can spread rapidly through the body. Knowing the differences and symptoms of each could save a dog’s life.

Causes of Pyometra in Dogs

Many causes of canine Pyometra exist; however, the most common is a result of the hormonal changes that an ‘intact’ dog goes through when experiencing estrus.

Repeat exposure to estrogen and progesterone cause the uterine walls to swell. An in-depth explanation is coming, but first, let’s go over a few key terms.

  • Estrogen – the type of female hormone produced in the ovaries.
  • Progesterone – the hormone that is created at the time of pregnancy.

The Decrease of White Blood Cells

Unspayed dogs continue to experience estrus, also known as heat, regardless of whether or not they are breeding. When a dog goes through the estrus cycle, there is a natural decrease of white blood cells from the uterus.

This reduction is necessary for the sperm to pass through the cervix thus resulting in the fertilization of the embryo. However, this decrease of white blood cells also makes the dog more susceptible to infection.

When a dog that is not breeding continues to have unnecessary decreases in their white blood cell count, bacterial infections become more and more likely to occur within the uterus.

Heightened Progesterone Levels

Dogs that go through estrus and do not become pregnant continue to have increased progesterone levels for the following eight to ten weeks after their estrus cycle.

The elevated progesterone levels cause the uterine lining to thicken in order to prepare for the expected pregnancy. This happens regardless of whether or not the dog is trying to breed.

In a healthy uterus, the body doesn’t react negatively due to its ability to proect itself from harmful bacteria. However, in a uterus that has continually gone through estrus cycles that haven’t resulted in pregnancy (thus creating extremely high progesterone levels), the ability for the muscles of the uterus walls to contract significantly decreases.

The inability of the uterine muscles to contract means that the body is unable to naturally eliminate bacteria, thus resulting in a fast-growing infection.

Cystic Endometrial Hyperplasia

Additionally, when pregnancy does not occur and the uterine lining continues to thicken, it oftentimes results in cysts in the tissues of the uterus. This medical condition, called Cystic Endometrial Hyperplasia, is the existence of pus-filled cysts inside a dog’s uterus.

As the cysts continue to develop and grow, they expel fluids and discharge that cannot pass due to the high levels of progesterone. The rapid influx of fluid results in bacterial growth and further infection.

Two Types of Pyometra

There are two types of Pyometra that you should familiarize yourself with: Open Pyometra and Closed Pyometra.

Open Pyometra

open pyometra

When Open Pyometra occurs, the uterus fills with fluid and deceased tissue and begins leaking out through the vagina. As the dog licks the area clean, additional bacteria is introduced through the cervix and into the uterus thus producing a secondary infection.

A healthy body’s automatic reaction to experiencing this secondary infection is to send white blood cells and additional fluid to the uterus. While the white blood cells aid in fighting the infection, the prior fluid accumulation continues to flow out of the vagina. This is known as Open Pyometra. Open Pyometra occurs when the cervix is open. Therefore, the uterus is able to naturally discharge fluid and excess debris through the vagina.

In Open Pyometra, since the cervix is open, fluids can flow freely from the infected area. Therefore, Open Pyometra is very treatable. In fact, you can oftentimes times it in the comfort of your own home.

Open Pyometra is generally easier to diagnose as a pet owner due to physical signs, primarily pus-like discharge. We’ll get into this more in a minute.

Closed Pyometra

closed pyometra in dogs

Conversely, closed Pyometra occurs when the cervix is closed. A closed cervix doesn’t allow for the necessary draining of fluids, thus causing the uterus to fill. As the uterus fills, bacteria forms, leading to infection. This toxicity can lead to the uterus bursting.

The rupture of the uterus forces the toxic fluids into the abdominal cavity. This contamination usually results in septic peritonitis and kidney failure. Even with aggressive medical attention, the dog often dies within forty-eight hours.

Closed Pyometra is more difficult to diagnose because there aren’t many physical symptoms as the pus is unable to escape.

Thankfully, catching Pyometra long before it becomes incredibly dangerous is very possible thanks to advances in science.

Signs of an Enlarged Uterus

Symptoms of Pyometra vary, based on whether the dog is facing open Pyometra or closed Pyometra.

Signs of Open Pyometra

  • Abdominal distension
  • Vaginal discharge (white, yellowish or green)
  • Foul-smelling vaginal discharge
  • Pus discharge
  • Excessive licking after the heat cycle
  • Personality changes such as aggression and depression
  • Drinking more water than usual
  • Pickiness with food or loss of appetite
  • Weakness in hind legs from the enlarged uterus

Due to the nature of these symptoms, they are easy to see and take action.

Signs of Closed Pyometra

  • Lethargic behavior
  • Excessive panting and difficulty breathing
  • Anorexia or loss of appetite
  • Vomiting
  • Fever often reaching 104 to 106 degrees
  • Increased water consumption
  • Extreme depression

If you notice any of these symptoms of Pyometra, take immediate action. While Pyometra usually develops two to four months after a heat cycle, once it begins it worsens rapidly. When the cervix is closed, symptoms of Pyometra may be harder to spot initially.

There is no time to spare in getting a proper diagnosis and treatment.

A veterinarian will diagnose Pyometra with:

  • X-rays
  • Abdominal ultrasound
  • Blood work to determine infection

Other Signs of Infection

depression in dogs with pyometra

Dogs are generally reluctant to show that they are feeling unwell. Therefore, if your dog begins to show clinical signs of illness, chances are they haven’t been feeling well for some time. Any signs that are uncharacteristic of your pup’s “normal” should be monitored.

Here is a list of some immediate signs of infection that a pet owner should look out for:

  • Sudden fever
  • Loss of Appetite
  • Depression
  • Lethargic behavior
  • Inability to move more than necessary
  • Stiffness in muscles
  • Vomiting
  • Diarrhea
  • Shivering
  • Excessive drinking
  • Excessive urination
  • Rapid dehydration
  • A runny nose
  • A spontaneous cough
  • Bloody vaginal discharge
  • Pus discharge the vagina, ears, eyes, or nose

Knowing the signs of a bacterial infection, in addition to signs of Pyometra, allow pet owners to seek medical attention and get their dog back on his or her feet quickly.

Treating Pyometra in Dogs

There are several treatment options available to treat Pyometra in dogs. Treatment is based on whether the cervix is open or closed, as well what stage the virus is in. The sooner that symptoms of Pyometra are noticed and the virus is caught, the more treatment options are available.

Surgical Treatment

surgical treatment for dogs with pyometra

The most common and preferred way to treat Pyometra is to remove the ovaries and infected uterus, surgically.

As far as surgeries go, an ovariohysterectomy can be more intricate than a typical spay once it reaches the stage of Pyometra. However, if Pyometra is caught early, most dogs are good candidates for the procedure.

If Pyometra is not caught early on, the dog will most likely be extremely ill, resulting in a much more complicated procedure.

Performing a lavage ( a process in which your vet will wash out a body cavity) of the uterus removes the pus and excess fluids and aids in the healing.

Additionally, a longer hospitalization is often mandatory, as well as intravenous fluids and antibiotics for two weeks after Pyometra surgery.

A board-certified veterinary surgeon may suggest additional treatment in addition to Pyometra surgery, depending on the severity of the virus.

Non-surgical Treatment


Aglepristone is a synthetic steroid used to disengage progesterone’s support of pregnancy. By blocking the progesterone receptors, the dog’s body can discharge naturally.

This treatment is a potential alternative to avoid surgery. Dogs may have pain at the injection site, but overall, it is a gentle procedure.


Prostaglandins are a group of hormones that lower the levels of progesterone, open the cervix, and allow the body to purge naturally.

Important Information Regarding Non-surgical Treatment

While many pet owners wish to avoid surgery, there are a few crucial points worth considering in regards to non-surgical treatment.

  • The treatment is not always successful.
  • Side effects include restlessness, vomiting, and abdominal pain.
  • If treatment does not work, the option for surgery may have passed, as the Pyometra virus grows and worsens.
  • Prostaglandins force the uterus to contract which could cause the uterus to split.
  • If the uterus ruptures, the fluids will spill into the abdominal cavity, resulting in immediate contamination.

Furthermore, based on statistics, non-surgical treatment may not be appropriate or even possible for your dog’s specific case.

  • The success rate for treating open pyometra is 75-90% in uncomplicated cases.
  • The success rate for treating closed pyometra is only about 25-40%.
  • The chance of the disease reoccurring is as high as 50-75%.

Not seeking treatment, surgical or non-surgical, is the worst thing you can do as a pet parent. If you do not implement treatment quickly, the results are generally fatal.

Based on the staggering statistics, surgery may make more sense to ensure that the dog will recover fully and heal.

How To Prevent Pyometra in Dogs

The best prevention of canine Pyometra is having your female dog spayed at six months of age but before the first heat cycle. Spaying too early has its own set of risks that we also want to prevent.


FYI – Spaying is the surgical procedure to sterilize a female animal by removing the ovaries. Neutering is also the surgical procedure to sterilize an animal but does not pertain to a specific gender. Therefore, we refer to spaying when talking about female animals and neutering when talking about male animals.

The vast majority of veterinarians strongly encourage spaying or neutering for a multitude of reasons. Reducing the overpopulation of dogs and cats that are unable to be cared for is a compelling reason for spaying. In fact, many humane societies make spaying mandatory when adopting a pet.

Also, spaying and neutering help to lower specific behavioral characteristics such as aggression and sexual habits like mounting. Not to mention, neutering prevents your furniture from constantly being peed on, as it is common for male dogs to “mark” their territory.

However, perhaps the most crucial reasons to spay or neuter your pup are unforeseen medical reasons. Many of these medical issues tend to result in required emergency surgeries.

The most life-threatening of these emergencies and arguably the most significant reason to spay your pup is Pyometra.

Stump Pyometra

The majority of dogs that are spayed early in their life will not experience Pyometra. However, in some cases, a Uterine Stump Pyometra could occur after an incomplete ovariohysterectomy.

Stump Pyometra happens when a part of the ovarian tissue remains present, and the dog experiences an increase of progestational hormones that it is unable to regulate.

Feline Pyometra

While this article primarily covers Pyometra in dogs, Pyometra in cats is also common and holds the same weight in severity if undiagnosed. Like dog Pyometra, you can avoid and treat Pyometra in cats if you find it early enough.

Words To Know

Medical and unfamiliar terminology can make a worried pet owner feel an additional amount of stress. We went through quite a bit of information when discussing dog Pyometra. Below is a list of terms that your vet may use freely, but may be confusing for the rest of us. Becoming familiar with what is going on with your pup can give any pet owner a glimmer of confidence in a very scary situation.

Progesterone Definition

Progesterone is a female steroid sex hormone that the corpus luteum (or an endocrine structure in female ovaries) releases. Additionally, progesterone stimulates the uterus and prepares it for pregnancy.

Estrus Definition

Estrus is another word for heat. ‘Intact’ female dogs go through an estrus cycle that is induced by reproductive hormones. When female dogs continually experience estrus and are not breeding, their bodies’ reaction can lead to Pyometra.

Pus Definition

Pus is a thick fluid, produced in infected tissue, that forms as part of an inflammatory response to infection. It is often yellowish or greenish in color. Pus consists of dead white blood cells, cellular debris, and necrotic tissue. Pus coming from any of your dog’s orifices is a telling sign that something is wrong.

Spay Definition

Spaying is the sterilization of a female animal by removing its ovaries. When Pyometra occurs, your vet will remove the infected uterus and ovaries in a more complicated spay, known as an ovariohysterectomy.

Cyst Definition

A cyst is an abnormal membranous cavity containing fluid. In closed Pyometra, these cavities can burst, causing fluid to fill the uterus.

Cervix Definition

The cervix is the lower portion of the uterus. It allows passage between the uterus and vagina and is a crucial part of female reproduction. The cervix is tightly closed except during the estrus cycle to allow for sperm to enter the uterus. An open cervix allows for the natural purging of the uterus. A closed cervix can lead to the uterus filling and bacterial infections occurring.

Bacteria Definition

Bacteria are microscopic living organisms that exist everywhere. A common misconception is that bacteria is dangerous. However, bacteria is necessary for the body and can actually be beneficial.

When You Know Better, You Do Better

dog with pyometra

We cannot stress enough the importance of knowing what is best for your beloved dog. Veterinarians have encouraged spaying and neutering a dog. However, only recently have science advancements shown exactly how detrimental not spaying your dog can potentially be.

The most important thing that a pet owner can do in order to avoid Pyometra is to spay their dog at six months of age, or before the first estrus cycle occurs. As female dogs get older, spaying involves more avoidable risks.

We know how much you love your dog. By staying up to date on new information as it becomes available, pet owners are able to see early signs of concern and act appropriately.

Perhaps the easiest way to ensure the best for your pet is to simply stay alert. Some dogs are more lethargic than others. Some dogs are picky food eaters while other devour everything in site. The importance of knowing your dog’s personality and characteristics is crucial in order to notice any changes.

Furthermore, if your dog shows clinical signs of being “off,” as pet owners, we MUST listen. As previously mentioned, dogs do not often show signs of being unwell until the illness has already progressed. Waiting to see if it passes can have devastating consequences.


Are there different types of Pyometra?

Are there non-surgical treatment options for Pyometra?

How can I make sure my dog doesn’t get Pyometra?

What are the signs of Pyometra?

What is the uterus and how is it affected by Pyometra?


About the author

Chelsea Hunt-Rivera

Chelsea Rivera is a Dedicated Pet Parent who loves to create amazing content for pet owners and is helping change pet wellness as the Head of Content for