All About Dangerous Canine Pyometra Infections

Sick little Terrier female

Canine pyometra is a life-threatening condition. Learn how to spot the signs as early as possible.

About Canine Pyometra

Pyometra is essentially an infection of the uterus. It can affect any unspayed female regardless of whether she has ever been bred. However, there does seem to be a higher rate of infection in older females. This might be attributed to the fact that the immune system tends to grow weaker as some pets age.

How Pyometra Is Contracted

During a female's heat cycle, her uterus opens slightly in order to release the blood discharge typically seen during the cycle and also permit the entry of semen if she happens to get bred. While the urterus is open, bacteria also have a chance to gain entrance.When the heat cycle ends, the uterus closes completely, and any bacteria that may have made their way in are trapped inside. In most cases, the dog's immune system is able to kill off the bacteria without incident, and life goes on normally. However, pyometra develops when the immune system is unsuccessful at fighting off the bacterial invaders.

As the condition develops, the infection eventually makes its way through the uterine walls and begins to circulate in the bloodstream. This results in a highly toxic situation for the dog, which has become quite sick by this point.

The onset of pyometra is typically noticeable between one and two months after the end of the heat cycle.

Types of Pyometra

There are two basic types of canine pyometra.

Closed Pyometra

The term "closed pyometra" refers to the condition when the infection develops inside the closed uterus. This type of pyometra is especially dangerous since it takes longer to realize something is wrong with the dog because there is relatively little outward sign until the infection is fairly far along.

Open Pyometra

The term "open pyometra" is used to describe the condition when the uterus actually remains slightly open rather than closing at the end of the heat cycle. This type of pyometra is easier to diagnose because there are visible signs of infection, such as a foul pus discharge released from the vulva.


As stated previously, noticing signs of canine pyometra can be more difficult to spot depending on which type of the infection a dog has. However, here is a list of all the signs to watch for.

  • A distended abdomen - This is the result of pus build up from the infection, and it can cause tenderness in the area. This symptom would become very obvious in a case of closed pyometra.
  • Pus discharge - Discharge can only be seen in a case of open pyometra. The fact that the uterus remains slightly open allows some of the discharge to drain via the vaginal opening. This means that the abdomen may not enlarge nearly as much since not all of the fluid is trapped. However, there may still be some enlargement on closer examination.
  • Foul odor - This comes directly from the discharge and is created by the anerobic bacteria that comprise the infection.
  • Fever - As with any infection, fever develops as the immune system attempts to fight off the invaders.
  • Dehydration - This typically develops as the result of a fever. You may observe increased thirst in an infected dog as a response to the fever, but her body will also increase urine output as it tries to flush out the infection. So, dehydration is often the result of the entire process.
  • Lethargy - An infected female will appear to be sluggish and sleepy as all her energy becomes directed at fighting the infection.
  • Loss of appetite - This is a common sign of many illnesses, and a case of canine pyometra is no exception. An animal that doesn't feel well for any reason may not feel like eating, so always take this as an early warning sign that needs to be paid the proper attention.
  • Vomiting - This can also be observed with a case of pyometra as well as many other illnesses. It may be due in part to the pain and increased pressure felt with a uterine infection.

Reaching a Diagnosis

Although you may begin to suspect a uterine infection has developed if you notice one or more of the symptoms listed above, you'll still need your vet's help to make a proper diagnosis and administer life-saving treatment.

In addition to looking for the symptoms, a vet will also gently feel the abdomen and perhaps even look for uterine abnormalities/enlargement via an ultrasound to reach a conclusive diagnosis. A blood test will also reveal toxins in the bloodstream.

Treatment Options

There used to be only one treatment option for a case of canine pyometra; hospitalization and surgical removal of the infected uterus and ovaries. This is still the most common method of treatment used today, and it effectively spays the dog. However, operating on a very sick dog makes surgery even more dangerous, and great care must be taken during the course of the operation to prevent the infection from leaking as the organs are removed. This is the only treatment option for a case of closed pyometra

A second option is to hospitalize the dog and adminster prostaglandins in an effort to force the uterus to contract and expel the pus infection. However, this treatment is only an option in a case of open pyometra, and it is the only chance to preserve the uterus for future breeding.

Antibiotics are usually administered with either treatment option to remove any traces of infection that may still be circulating in the dog's system.

Early detection can help a dog survive pyometra, but the animal will certainly die without proper treatment. If you have an unspayed female, it pays to be a little vigilent after each heat cycle ends.

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All About Dangerous Canine Pyometra Infections