What Age Do Female Dogs Get Pyometra?

Pyometra is a serious and potentially life-threatening inflammatory infection of the uterus that primarily afflicts unspayed female dogs. It involves the accumulation of pus in the uterus, and can lead to sepsis, organ failure, and death if left untreated. Knowing the typical age pyometra occurs is critical for dog owners and veterinarians to monitor for early signs and intervene quickly. Since pyometra has nonspecific signs like lethargy and vomiting, awareness of the typical age onset can raise suspicion for pyometra as the cause.

What is Pyometra?

Pyometra is an infection of the uterus that occurs in female dogs. According to the American College of Veterinary Surgeons, pyometra is defined as an “accumulation of pus within the uterus.” It typically occurs in dogs that have not been spayed and is considered a common condition in middle-aged or older intact female dogs. However, pyometra can also occur in young dogs.

The infection leads to inflammation of the uterine lining and an accumulation of pus in the uterus. Bacteria, usually E. coli, enter the uterus through the cervix and proliferate rapidly due to hormonal changes. As the bacteria multiply, the cervix closes to block drainage and a potentially life-threatening condition develops. Left untreated, pyometra can be fatal.


The symptoms of pyometra in dogs can include:

  • Vaginal discharge – This is often the first symptom noticed. The discharge is typically purulent and can range from light to heavy. (VCA Animal Hospitals)
  • Lethargy – Dogs with pyometra will often act very lethargic and depressed. They have little energy or interest in exercise or play. (Cornell University)
  • Loss of appetite – Affected dogs tend to lose their appetite and may refuse food and treats.
  • Frequent urination – Some dogs with pyometra urinate more frequently due to the effects of the infection on the kidneys.
  • Vomiting or diarrhea – In some cases, the infection can cause vomiting or diarrhea.
  • Enlarged abdomen – The infected uterus swells up with pus, which may enlarge the abdomen.

If pyometra is suspected based on symptoms, prompt veterinary care is essential. Left untreated, pyometra can be fatal.


Pyometra is caused by bacterial infection of the uterus, most commonly with Escherichia coli. The infection develops when progesterone levels remain elevated after estrus, preventing the cervix from contracting and causing drainage of uterine contents. This leads to an accumulation of fluid and bacteria inside the uterus.

There are several factors that increase a female dog’s risk of developing pyometra:

  • Age – Older dogs are at higher risk. Most cases occur in dogs over 4 years old.
  • Breed – Some breeds like Golden Retrievers, Rottweilers, Cavalier King Charles Spaniels and Bernese Mountain Dogs are more prone to pyometra.
  • Hormones – Dogs that have not been spayed are at increased risk since progesterone levels remain elevated after heat cycles, predisposing the uterus to infection.
  • Number of heat cycles – Risk increases with each heat cycle, so dogs that have had multiple cycles are more likely to develop pyometra.
  • Uterine disease – Conditions like cystic endometrial hyperplasia make the uterine environment more hospitable to bacteria.

Therefore, female dogs that are unspayed, older, and have had multiple estrus cycles are most likely to develop pyometra. The elevated progesterone prevents drainage of uterine contents after estrus, allowing bacterial overgrowth.


Pyometra is diagnosed through physical examination, medical history, bloodwork, imaging tests, and analysis of vaginal discharge. The veterinarian will check for common symptoms like vomiting, lethargy, increased thirst and urination, and vaginal discharge which can indicate pyometra (1). They will also feel the abdomen to check for any enlargement or fluid-filled structures which may point to an infected uterus (2). The veterinarian will ask about the dog’s recent heat cycles and if she was spayed, since pyometra usually occurs within 2 months after a heat cycle in unspayed dogs (3).

Initial screening blood tests like a complete blood count, biochemistry profile, and urinalysis can reveal increased white blood cells, toxic levels of bacteria in the blood, and other abnormalities that may suggest pyometra (1). Diagnostic imaging such as abdominal ultrasounds or x-rays allow visualization of the enlarged, fluid-filled uterus in pyometra cases (2). Samples of the vaginal discharge are also examined under the microscope which typically shows large numbers of degenerative neutrophils and bacteria in pyometra (3). Surgical exploration of the abdomen may be necessary for a definitive diagnosis in some cases (1).


The most effective treatment for pyometra is surgery to remove the uterus and ovaries, also known as an ovariohysterectomy or spay. According to the veterinarians at Cornell University’s College of Veterinary Medicine, “Any female dog that has not been spayed is at risk for developing pyometra” (https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/pyometra). Surgically removing the infected uterus eliminates the source of infection and prevents recurrence of the condition.

Veterinarians may also consider medical treatment with prostaglandin shots and antibiotics in some cases. However, this does not remove the diseased uterus and carries a higher risk of recurrence. According to VCA Hospitals, “The preferred treatment is to surgically remove the uterus and ovaries by performing an ovariohysterectomy (spay)” (https://vcahospitals.com/know-your-pet/pyometra-in-dogs).

In severe cases where the dog is unstable, stabilized with intravenous fluids and antibiotics may be necessary before surgery can be performed. Close monitoring and supportive care are crucial, as pyometra can quickly become life-threatening without proper treatment.

Age of Onset

Research shows that pyometra most commonly occurs in middle-aged to older female dogs. While it can occur in dogs of any age after their first heat cycle, the average age of onset is between 4-10 years old.

One study found the mean age of dogs presenting with pyometra to be 9.36 +/- 0.38 years old (1). Another survey showed the average age was 2.4 years, but this was attributed to the young age of the study population (2).

According to VCA Animal Hospitals, pyometra typically occurs in older dogs, but may happen in any intact young to middle-aged dog after their first heat cycle (3).

In summary, the typical age range for pyometra onset in dogs is 4-10 years old, with most cases occurring in middle-aged to older dogs. While it can occur earlier, the risk increases with age for intact female dogs.


The most effective way to prevent pyometra is to get your female dog spayed (referenced from Pyometra: Preventing & Addressing A Common Issue …). Spaying involves surgically removing the uterus and ovaries, eliminating the possibility of pyometra developing. According to research, dogs spayed before their first heat cycle have a 0.5% chance of developing pyometra, compared to those spayed after their first heat cycle which have an 8% chance (Pyometra).

Veterinarians recommend spaying female dogs before their first heat, ideally around 6 months of age. This prevents the influence of hormones that trigger pyometra. Spaying protects against life-threatening complications of pyometra including sepsis, shock, and kidney/liver failure (Pyometra in Dogs: Causes, Treatment and Prevention). While spaying has risks like any surgery, the benefits far outweigh potential complications when it comes to preventing pyometra.


The prognosis for dogs with pyometra depends greatly on whether it is treated or left untreated. According to research, the survival rate for dogs with pyometra that undergo ovariohysterectomy (OHE) surgery is very high at around 97% (Pailler, 2022). This indicates that the prognosis is very good if surgical treatment is pursued. However, without treatment the prognosis is extremely poor. Pyometra can quickly become deadly if left untreated due to the toxic effects of the infection spreading. One source indicates the chance of successful resolution without surgery or other treatment is extremely low (VCA Hospitals). Another confirms that untreated pyometra can be fatal from the overwhelming infection (Cornell). Therefore, while the prognosis with treatment is very positive, dogs face a high risk of death if pyometra is left untreated.


Pyometra is a serious and life-threatening condition that affects female dogs who have not been spayed. While it can occur in dogs of any age, it typically affects middle-aged to older dogs between the ages of 4 and 10. The exact causes of pyometra are not fully known, but it is linked to hormonal changes in the reproductive tract and the influence of progesterone. Without prompt treatment, pyometra can be fatal within days due to the systemic illness it causes through the spread of infection.

The classic symptoms of pyometra include lethargy, vomiting, excessive thirst, and abdominal distension. However, the symptoms can sometimes be vague, so veterinary examination and diagnostic testing are crucial. Treatment usually involves emergency surgery to remove the infected uterus and ovaries. Dogs who recover from pyometra should be spayed to prevent recurrence. The preferred way to prevent the disease altogether is to have the dog spayed before her first heat cycle.

In summary, pyometra typically affects unspayed middle-aged to older female dogs. Prompt diagnosis and treatment is essential for the best prognosis. Spaying dogs at a young age prevents the disease from developing later in life. Being aware of the signs and risk factors for pyometra allows owners to seek timely veterinary care for affected dogs.

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