Pyometra in Dogs

Barri J. Morrison, DVM
By Barri J. Morrison, DVM on Oct. 26, 2023
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In This Article


What Is Pyometra in Dogs?

Pyometra in dogs is a highly severe and potentially life-threatening infection of the uterus. In female dogs affected by this condition, the uterus becomes inflamed.

This infection causes the formation of an abscess or the accumulation of pus within the uterus, which results in the dog becoming very ill.

With pyometra, toxins and bacteria can infiltrate the wall of the uterus and then leak into the bloodstream. This accumulation of infection can quickly cause the tissue of the uterus to die.

This tissue death (necrosis) can ultimately lead to a rupture of the uterus, causing large amounts of pus to be spilled into the abdominal cavity.

Additionally, the buildup of toxins in the body can adversely affect the dog’s kidneys, potentially causing kidney failure. Without prompt and effective treatment, this condition can be fatal.

Pyometra usually occurs two to eight weeks after a female dog’s heat (estrus) cycle. Unfortunately, it is a common condition in dogs who are not spayed and occurs in up to 25% of them.

The good news is that this condition is very preventable by having your dog spayed when she is a puppy. Spaying removes the uterus and the source of the female hormones that drive the infection.

Pyometra is a medical emergency. If you suspect your female dog is affected, she needs to be seen by her veterinarian or an emergency veterinarian as soon as possible.

Symptoms of Pyometra in Dogs

The common symptoms of pyometra in dogs include:

Causes of Pyometra in Dogs

Pyometra can occur at any point in an unspayed female dog’s life after she has started her heat cycle, or she has become sexually mature.

Pyometra can happen at any age but more commonly occurs in dogs that are more than 5 years old, after many heat cycles have produced significant changes to the female reproductive system over time.

Pyometra is a uterine infection caused by hormonal changes in a female dog’s reproductive system. It commonly occurs shortly after a dog’s heat cycle when high levels of progesterone are still present, which is necessary to help the body prepare for a possible pregnancy.

Progesterone causes thickening of the lining of the uterus, creating ideal conditions for bacteria to grow. It also decreases the ability of the muscles of the uterus to contract and remove any accumulated fluids or bacteria, as it should with a normal heat cycle.

Researchers believe that E. coli, the primary bacteria causing pyometra in dogs, enters the uterus after ascending from the intestinal tract. E. coli accounts for 57–100% of pyometra cases in dogs.

In recent years, there has also been an increase of pyometra in dogs who are fed raw meat. This can increase the number of bacteria present in a dog’s stool, primarily salmonella and E. coli.

A decreased amount of white blood cells in the uterus also contributes to pyometra. White blood cells play a key role in removing infections from the body.

During a dog’s heat cycle, these white blood cells are inhibited from entering the uterus. This is a normal protective mechanism to allow sperm to safely enter the uterus without being destroyed by the white blood cells.

The combination of increased hormones and decreased white blood cells often leads to life-threatening pyometra in dogs. Pyometra can also occur in unspayed female dogs who have been given estrogen or progesterone medications.

A common misconception about pyometra in dogs is that you can always see pus coming from the vagina, but this isn’t true. The cervix is usually tightly closed, except when a dog is in or recently has been in heat.

When the cervix is open and the uterus is thickened, it creates the perfect environment for bacteria to enter the uterus and multiply. There are two kinds of pyometras categorized by the state of the dog’s cervix.

 An open cervix will allow pus, with or without bloody discharge, to exit from the vagina. With a closed cervix there is no vaginal discharge present, and the enlarged uterus can cause a distended abdomen. A closed pyometra will progress much faster than an open pyometra.

This situation is far more serious because it can often be confused with many other disease processes, leading to delays in diagnosis and treatment.

Open pyometras are more common than closed ones.

How Veterinarians Diagnose Pyometra in Dogs

Pyometra is diagnosed by a variety of factors, including a physical examination.

If there is vaginal discharge present, a sample can be collected and analyzed under a microscope to detect the presence of bacteria and other cells present right after estrus.

Your veterinarian will likely also recommend some imaging, such as ultrasound or X-rays of the abdomen, to look for the distended, fluid-filled uterus.

Bloodwork is also performed to look for evidence of infection and potential kidney involvement.

Treatment of Pyometra in Dogs

Pyometra is a medical emergency and requires immediate treatment.

The primary treatment for pyometra is spaying the affected dog. This is a surgical procedure called an ovariohysterectomy, which involves removal of the uterus and ovaries.

Extreme caution is taken during the surgery to make sure that pus and bacteria are not spilled into the abdominal cavity. Because pyometra surgery is considerably more complex than a routine spay on a healthy dog, it typically costs five to 10 times more.

If the uterus has already ruptured and there is pus in the abdominal cavity, your vet will need to flush the abdomen repeatedly during the surgery to prevent sepsis, a systemic infection caused by bacteria in the blood. Antibiotics are also given during and after surgery to help prevent sepsis.

Pain medication is given during and after the operation as well, to help manage the dog’s discomfort.

Depending on how sick they are or have become, dogs will need to stay hospitalized for a few days or longer for IV fluids and other medical treatments.

There is an alternative treatment available for a dog with pyometra, but it is generally not recommended.

This alternative is considered when a pet parent still wants their dog to be able to reproduce and have puppies. Even if these treatments are successful, they leave the dog highly vulnerable to another pyometra, so she needs to be monitored very closely.

The alternative treatment involves the use of prostaglandin, a hormone that can be given by injection. It is used to induce uterine contractions to expel the pus from the body. These injections can be attempted only in cases of open pyometra, not closed ones.

After receiving prostaglandin injections, the dog must be bred and go through a successful pregnancy during their next heat cycle or the reoccurrence rate of the pyometra is very high, estimated at 77%.

Without surgery or a successful prostaglandin injection, it is nearly impossible for a dog to recover from pyometra. If treatment is not performed as soon as possible, the toxic bacteria will be fatal.

Recovery and Management of Pyometra in Dogs

During recovery from surgery, it’s important that you monitor your dog very closely. Recovery usually takes a few weeks, but it can be longer if your dog is very ill.

She should wear a protective collar or surgical suit to ensure she cannot lick her incision. Antibiotics are given for at least two weeks after surgery.

It’s also recommended that your dog be on strict rest during this recovery period of at least two weeks after surgery.

She should not be allowed to run, jump, or roughhouse, as that can put tension on the surgical incision, causing an infection or causing the incision to open.

It might even be a good idea to keep her crate-rested for the recovery period, especially if there are other pets in the house who might disturb her incision.

If the incision opens, your dog might need another surgery to repair it. Often, your vet might prescribe pain medication that doubles as a sedative as well to help keep your dog as relaxed as possible while she heals.

Pyometra in Dogs FAQs

How long can a dog survive with pyometra?

Without surgery or a successful prostaglandin injection, it’s very unlikely that a dog will recover from pyometra. If treatment is not performed as soon as possible, the toxic bacteria will be fatal.

What are the earliest signs of pyometra in dogs?

The earliest signs of pyometra can be nonspecific, meaning that they do not automatically point to an infected uterus.

These signs include lethargy, vomiting, and a change in appetite, with or without vaginal discharge.

Featured Image: SeventyFour/iStock / Getty Images Plus via Getty Images

Barri J. Morrison, DVM


Barri J. Morrison, DVM


Barri Morrison was born and raised and currently resides in Ft. Lauderdale, Florida. She went to University of Florida for her...

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