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Another Reason to Spay Female Pets

Pyometra, or infection in the uterus, is a serious, life-threatening condition in pets. Preventing this condition is an important reason for routine spaying of female dogs and cats.

During estrus or "heat" in an intact female, white blood cells are decreased in the uterus to allow sperm to pass safely. After estrus, progesterone levels remain high for 8-10 weeks causing thickened uterine lining and decreased ability of uterine walls to contract.

  Cat, Dog and Heart
Spay your female pets to prevent pyometra, a life-threatening condition.

With repeated cycles, the uterine lining forms cysts in it, creating an ideal environment for bacteria to grow. The cervix, which is normally closed, is open during estrus. Bacteria normally found in the vagina can enter the uterus. With thick cystic walls, bacteria can grow more easily and are not expelled.

Pyometra is much more common in older un-spayed females due to the changes in the uterine wall. However, it also may occur in younger or middle-aged dogs. It typically occurs 2-8 weeks after estrus.

Clinical Signs of Pyometra

The classic pyometra patient may exhibit the following symptoms:

  • poor appetite
  • fever
  • lethargy
  • appears emaciated
  • vomiting
  • drinking excessively

In an open pyometra, the cervix is open and a malodorous vaginal discharge is seen.

With a closed pyometra, in which the cervix is closed, there is no vaginal discharge and diagnosis may be more difficult. These patients tend to become severely ill rapidly, since they have retained all the uterine contents. Toxins from the bacteria affect the kidneys causing increased urine production and increased drinking.


Clinical signs suggest pyometra in an older un-spayed female. The diagnosis is supported by a marked elevation in the white blood cell count. Affected pets also have a low specific gravity of the urine. Radiographs of the abdomen often confirm the diagnosis by identifying the enlarged uterus.


Recommended treatment is to surgically remove the ovaries and uterus. This is called an ovariohysterectomy or spay. Intravenous fluids and antibiotics are often needed before and after surgery.

While it has the same end result as routine spaying, a pyometra spay is far from routine. The surgery is more challenging and the patient is ill and often unstable. Therefore pyometra surgery and treatment typically costs five to ten times as much as a routine spay.

Possible complications with pyometra include:

  • Peritonitis, or infection in the abdominal cavity
  • Rupture of the uterus in surgery
  • Sepsis or disseminated intravascular coagulation (DIC) are uncommon complications which can occur before, during, or after surgery in response to the bacteria
  • Acute kidney failure

Prevention of Pyometra

The good news is that this condition is completely preventable by spaying female pets before pyometra develops. Often owners fear that their pet is too old to be spayed if it wasn't done during the first year of life. But a female cat or dog can benefit from spaying at any age.

Dr. Jeanette Asuncion is an associate at Illiana Veterinary Hospital in South Holland, IL. Originally from the Detroit suburbs, Dr. Asuncion earned a DVM degree from Michigan State's College of Veterinary Medicine in 1990.