A Pyometra is an infection in the uterus. This condition is serious and can be life threatening. Prompt veterinary care is imperative. It is a disease that is 100% preventable by spaying your pet.


Throughout a normal heat cycle (estrus), the uterus goes through many changes. White blood cells are inhibited from entering the uterus, which normally protect against infection. Increased hormone levels cause a thickening of the uterine wall. If pregnancy does not occur, the lining can form cysts which secrete fluid. The muscle walls are unable to contract and expel accumulated material. The combinations of these changes in the uterus make it a perfect environment for bacteria to flourish, leading to infection.


How do bacteria get into the uterus?

The cervix is the entrance to the uterus. It remains tightly closed except during estrus, when it relaxes to allow sperm to enter the uterus to fertilize the eggs. If the cervix is open or relaxed, bacteria that are normally found in the vagina can enter the uterus easily.


When and to whom does pyometra occur?

Pyometra may occur in any intact (not spayed), young to middle-aged female. It is most common in older pets that have had many estrus cycles without pregnancy, though it also occurs in females that have had litters. Pyometra usually occurs two to eight weeks after the last estrus.



Symptoms may vary for each patient and also depend on whether the cervix remains open or closed.

Open Pyometra: Pus or abnormal discharge may drain from the vagina. The pet often can be observed to lick frequently and excessively at their vulva. The pet may have a fever, be lethargic or depressed, and not want to eat. They may also show increased thirst and/or increased urination.

Closed Pyometra: Pus will collect in the uterus causing the abdomen to distend. The pet may stop eating, become lethargic and depressed. Vomiting and diarrhea may also be present. The bacteria release toxins in the body causing the pet to become ill very quickly. These toxins can harm the kidneys, which can cause the pet to drink excess water and produce more urine.



Diagnosis can be made by the veterinarian based on one or more of the following:

Medical history- Intact female, recently in heat, increased thirst and/or urination, showing signs of illness.

Physical exam- Discharge from the vulva, distended and/or tender abdomen, and fever may be observed.

Blood work- The white blood cell count will likely be increased.

Radiograph- Often the uterus can be observed on radiograph due to its enlarged size which will displace other organs in the abdomen.

Ultrasound- Uterus may be enlarged, be fluid filled, and/or have thickened walls.

 Lily Boser 3

How is pyometra treated?

The preferred treatment is to surgically remove the infected uterus and ovaries, also known as an ovariohysterectomy (“spay”). Early diagnosis of the disease can lead to a better outcome. Pets that are already quite ill can have more surgical complications and a longer period of hospitalization. The surgery is more complicated than a routine spay. Intravenous fluids are often required to stabilize the patient before and after surgery. Antibiotics are usually given during and after surgery.


Is there a treatment other than surgery?

There is another option to treating pyometra using hormone treatment. The success rate is low, the risks and potential long-term complications are high, and the side effects are often severe.


What happens if a pyometra is not treated?

The success rate of treating a patient without surgery is extremely low. The toxins from the bacteria can overwhelm the kidneys, which remove waste from the bloodstream, leading to kidney failure. If the cervix is closed, the uterus may rupture spilling pus into the abdominal cavity. The patient will become septic and can result in death within 48 hours.

Example: A normal uterus in a 40 pound dog will weigh approximately two to four ounces. The uterus is made up of a body with two horns. The horns of a normal uterus are smaller than a pencil. In the case of a pyometra, the same uterus can grow to one to four pounds and be the circumference of a large zucchini or squash.



Pyometra can be easily prevented by having your female pets spayed. If you do not plan to breed your pet, spay them at an early age, about 6 months. Females intended for breeding should be spayed as soon as they are retired. The age of retirement depends on the breed, but a general recommendation is 7 years of age or younger.

If you notice any of these symptoms in your pet, please contact your veterinarian promptly. Call Bemidji Veterinary Hospital at 751-2753.

This is Lily, a recent Pyometra surgery patient. She was hospitalized on antibiotics and IV fluids for 4 days following her surgery. She has been discharged into the care of her family and is making a full recovery. She had such a wonderful smile, we just had to share.

Lily BoserLily Boser 2