Pyometra in Cats

What is pyometra and how does it occur?

In simplest terms, pyometra is an infection in the uterus. It is considered a serious and life threatening condition that should be treated quickly and aggressively.

Pyometra occurs as a secondary infection because of hormonal changes in the female’s reproductive tract. During estrus or ‘heat cycle’, progesterone levels remain high for many weeks; causing the thickening of uterine wall lining in preparation for pregnancy. If pregnancy does not occur for many heat cycles, the lining of uterine wall keeps increase in thickness and cysts are formed in the uterus. This condition is called cystic endometrial hyperplasia. The thickened, cystic lining of the uterus secretes fluids that create good environment for the bacterial growth, high levels of progesterone hormone hinders the ability of the muscles in the wall of the uterus to contract and expel the fluids that was accumulated inside uterus.

During estrus, white blood cells are not allowed to enter to the uterus; this normally happens inside the uterus to allow sperms to enter the female’s reproductive tract without being damaged or knock down by white blood cells. Mostly the combination of these factors leads to an infection.

What else can cause changes in the uterus?

The use of drugs based on progesterone hormone can produce changes in the uterus alike to the estrus cycle. Beside, estrogen hormone or synthetic estrogen drugs will elevate the effects of progesterone on the uterus. Estrogen and progesterone based drugs are used to treat certain reproductive disorders. Any intact female who is receiving estrogen, progesterone hormones must be carefully monitored for the development of pyometra.

How do bacteria get into the uterus?

The cervix is an arch to the uterus. It remains tightly closed except during estrus, when it opens to allow sperm to enter the uterus.

If the cervix is open, bacteria that are normally present in the vagina can enter the uterus very easily. If the uterus is normal, the uterine environment is unfavorable for bacterial survival; however, when the uterine wall is not normal, fluids produced by wall of uterus produce perfect conditions for bacterial growth. In addition, when these abnormalities exist, the muscles of the uterus cannot contract normally either due to thickening of the uterine wall or the hormone progesterone. This means that bacteria that enter the uterus cannot be expelled out.

What are the clinical signs of pyometra?

The clinical signs vary whether the cervix is open or not. If it is open, pus will come from the uterus via vagina to the outside. This discharge may be observed on the skin or hair under the tail, or on bedding and furniture where the animal has laid recently. Because cats are usually much concerned with cleanliness, the discharge is usually cleaned up before it can be seen. With an open pyometra, lethargy, anorexia, fever and depression may or may not be present.

If the cervix is closed, the pus that forms is unable to come out to the outside. It collects inside the uterus causing distention of the abdomen. Toxins are released in the blood circulation by the bacteria. Cats with closed pyometra become severely ill in a short time frame. Typical signs would be anorexia, restless, and very depressed. Vomiting or diarrhea may also be present.

Kidneys are affected by the toxins released by bacteria and decrease the ability to retain fluid in body; it causes an Increase in urine production, and the cat drinks excess of water to compensate. This occurs in both open- and closed-cervix pyometra.

How is pyometra diagnosed?

In an early stage of the disease cat may have a slight vaginal discharge and shows no other signs of illness. But, most cats with pyometra will show illness later on. Mild sick female cat that is drinking more amount of water and that has not been spayed should be suspected of having pyometra. It is possible to have a vaginal discharge or a painful, enlarged abdomen.

Cats with pyometra usually have a high count of white blood cells and often have globulins. The specific gravity of the urine is very low due to toxins and their effect on kidneys..

If the cervix is closed, radiographs (X-rays) of the abdomen will show the enlarged uterus. If the cervix is open, uterus will not show enlargement in X-Ray. An ultrasound examination is advised in identifying an enlarged uterus.

How is pyometra treated?

“The advised treatment is surgical removal of uterus and ovaries(ovariohysterectomy).”