Pyometra is a disease that occurs when the uterus in an older female dog or cat fills with pus. Most affected dogs and cats are older than six years of age and have not been spayed or still have their ovaries and uteruses. Some spayed dogs can get an infection from a remnant of the uterus, which is called a stump pyometra.

The cause of a pyometrais an interaction between the lining of the uterus and the hormone progesterone. After a heat cycle takes place, the ovary releases progesterone to prepare the lining of the uterus for pregnancy. In older animals, this causes a syndrome called Cystic Endometrial Hyperplasia, in which the tissue that lines the uterus becomes excessive or persistent. As fluid accumulates along the lining of the uterus, bacteria can ascend from the vagina and the uterus becomes inflamed and ultimately infected and filled with pus. This infection can spread to other parts of the animal’s body, causing the animal to become systemically ill as well.

The clinical signs for a pyometra can be varied. The first clinical signs are usually seen within 4 weeks after a heat cycle in cats and 8 weeks in dogs. A vaginal discharge is the best indicator of a pyometra but will only be present if the cervix of the uterus is open. If the cervix of the uterus is closed, no vaginal discharge will be present. Other clinical signs of a pyometra include decreased appetite, lethargy, depression, vomiting, and diarrhea. Another unique clinical sign with a pyometra may be a sudden increase in drinking and urination. An endotoxin produced by the bacterial component of a pyometra, E. coli, causes a temporary paralysis of the kidneys’ ability to concentrate urine. This loss of concentrating ability for the urine causes the animal to suddenly drink excessive amounts of water.

The diagnosis of a pyometra involves a combination of history, clinical signs, and diagnostic tests. Since the timing of a pyometra is typically 4-8 weeks following a heat cycle, it is important to know when the last heat occurred. Physical exam findings such as distended abdomen and purulent vaginal discharge can support a diagnosis. Finally, more advanced diagnostic tests can help confirm a diagnosis. A complete blood count can show an elevated white blood cell count which would support a diagnosis. Abdominal X-rays may show tubular, fluid-filled structures in the area of the uterus. An ultrasound is also helpful to assess size, thickness, and presence of fluid in the uterus.

Treatment for a pyometra involves surgically removing the uterus and ovaries. The surgery can be a challenge because the severe infection that takes place during a pyometra does not make the pet an ideal anesthetic candidate. Depending on how severe the systemic extent of the disease is, extended hospitalization, including aggressive fluid therapy and intravenous antibiotics, may be necessary to overcome the illness. Animals surviving surgical correction of the problem have an excellent prognosis.

Pyometra is almost entirely a preventable disease. Spaying your dog and cat before 6 months of age will prevent the disease from taking place.