Pyometra in Cats

Causes, Treatment, and Prevention

Cat held by nurse in blue scrubs with a stethoscope.
Cats with pyometra can be very sick.

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Pyometra in cats is a serious type of uterine infection that can affect females that have not been spayed and typically occurs around 6 to 24 weeks after they are in heat. The infection is bacterial and usually migrates from the cat's vaginal tract. If left untreated, pyometra can be fatal. Knowing the symptoms of a cat with possible pyometra can help save its life.

What Is Pyometra?

Pyometra is a secondary condition that occurs because of the female cat's changing hormones in the reproductive tract which creates an environment for a bacterial invasion, most often by certain strains of E. coli.

There are two types of pyometra infections commonly seen in cats: open and closed. Open pyometra occurs when the cervix is open so some pus can drain out. If the infection is closed, the cervix is shut tightly so the pus can't drain and instead will cause the uterus to distend and eventually rupture.

Cats that have been spayed and have had their uterus and/or ovaries removed can't have pyometra unless the surgical procedure was incomplete. This uncommon type of pyometra that may occur on a spayed cat with some remaining ovarian tissue is referred to as a stump pyometra.

Symptoms of Pyometra in Cats

Signs will vary depending on whether your cat has an open or closed pyometra infection. Some of the symptoms are non-specific that can indicate many types of illnesses. Symptoms will persist as your cat's illness progresses and you should immediately call your veterinarian for an appointment.


  • Bloody or purulent vaginal discharge
  • Bloated abdomen
  • Lethargy and anorexia
  • Vomiting and diarrhea
  • Increased urination
  • Increased thirst
  • Excessive licking at the vaginal opening

Bloody or Purulent Vaginal Discharge

An open pyometra infection will commonly result in vaginal discharge. You may not be able to see the discharge on the cat's fur since your pet will have quickly cleaned it up. However, you may be able to spot it on her bedding, furniture, or possibly on the fur under the tail.

Bloated Abdomen

A closed pyometra infection does not have an open, draining cervix so the infection and pus stay in the uterus causing a bloated abdomen and results in a cat that feels very ill.

Lethargy and Anorexia

In both open and closed pyometras, the bacteria involved will release toxins that can cause systemic illness. This results in a cat that's listless and unwilling to eat.

Vomiting and Diarrhea

If sepsis (extreme response to the infection) has occurred, the cat may experience vomiting and diarrhea, which will also lead to dehydration and make the cat feel very ill.

Increased Urination

Your cat may begin to change its litterbox habits as a result of the malaise and start to urinate outside of the box. The bacteria's toxins circulating in the cat's body will also affect the kidneys' function. The kidneys will be unable to hold fluid and this will increase a cat's urine production. This symptom can occur in both open and closed pyometra infections.

Increased Thirst

A cat with this infection may have an increased thirst due to the toxins in the uterus affecting the kidneys and causing increased water loss.

Excessive Licking at the Vaginal Opening

If the cat has an open pyometra and the cervix is open, she may lick at the vaginal opening frequently to clean the draining infection.

Causes of Pyometra

The cause of pyometra is not fully understood, but seems to depend on several factors happening concurrently. A cat in heat will have a thickened uterine lining in preparation for a potential pregnancy. After several cycles of a thickened lining but no pregnancies, cysts will form in the lining of the uterus. At the same time, when a cat is in estrus (in heat), the opening to the uterus opens to allow sperm to enter during mating. But sometimes bacteria in the vaginal tract of a cat can also enter the uterus during a heat cycle.

The cysts in the uterus will secrete fluids that allow bacteria to grow, cause an infection, and develop pus. The additional progesterone in the cat's system to keep the thick lining also prevents the uterus from expelling fluids and bacteria. The extra progesterone is also meant to help keep white blood cells out of the uterus so sperm can stay safe. All of these factors can result in pyometra.

Not every cat with a uterus will get a pyometra infection. However, older cats with thickened uterine linings due to having gone through several heat cycles and cats with abnormal or cystic uterine linings are more at risk for contracting pyometra. This is because of the body's inability to get rid of the infection like a normal, healthy uterus would do.

Diagnosing Pyometra in Cats

A veterinarian will perform a full physical examination along with obtaining a medical history of your cat. If there is no evidence that your cat has been spayed and is showing signs of pyometra, tests will be recommended. These tests can typically all be performed in a short amount of time in the animal hospital. Tests that will be recommended include the following:

  • Blood tests will show if the white blood cell count and certain proteins in the blood are elevated.
  • A vaginal cytology will show if there are bacteria and white blood cells present.
  • X-rays or ultrasounds will show an enlarged uterus.


If a pyometra is diagnosed in your cat, surgery will be necessary to remove the infected uterus and ovaries. The surgery is more complex than routine spaying because care needs to be taken so that the enlarged uterus does not leak or rupture upon removal. Most cats with pyometra will also have signs of sepsis, requiring additional stablization before surgery and a longer stay in the hospital after surgery.

Though often not the preferred treatment, a medical option without surgery is a possibility. Your veterinarian can offer prostaglandins, a group of hormones that will allow the progesterone to recede and open the cervix to expel the infection. The results are spotty and it is not advisable for a severely ill cat.

Prognosis for Cats With Pyometra

Antibiotics and pain medications will be prescribed as well to help your cat recover from the infection and surgery. A surgical outcome can be very favorable if there was no contamination of the abdomen during surgery. Some cats will have sustained permanent kidney damage due to the infection, even after surgery, which will result in excessive urination and an increase in drinking water.

How to Prevent Pyometra

The only way to prevent pyometra from occurring in your cat is to have it spayed. This surgery will remove either both the uterus and the ovaries or just the ovaries so that a cat cannot go through a heat cycle. Without the hormones that are released from the ovaries during a heat cycle or a uterus that can get infected, a cat cannot develop a pyometra infection. Spaying a cat is a commonly recommended procedure for this and other health reasons.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
Article Sources
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