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Pyometra in Cats - Causes, Symptoms & Treatment

What is pyometra?

Pyometra (pus-filled uterus) is a serious and  life-threatening infection associated with a condition known as "cystic endometrial hyperplasia (CEH)". It used to be thought that female cats were induced ovulators, meaning ovulation occurs when the cat mates, however, it is now believed that the female may ovulate spontaneously (without mating) and several ovulations may have occurred without the owner being aware. It is also speculated that even mild stroking of the queen in heat may be enough to induce ovulation.

Normally if no pregnancy occurs, the lining will regress at the end of the heat cycle, however, frequent heat cycles, spontaneous ovulation and administration of progestins (used to control heat cycles in cats) may result in abnormal endometrial growth.   In this situation, prolonged exposure to progesterone results in hyperplasia (enlargement) of the endometrium and causes the endometrium glands to become cystic. Other influencing factors such as the inhibition of myometrial (uterine wall) contractions, the cervix is closed, white blood cell activity is decreased at this time, creating an ideal environment for bacteria to grow. E. coli and Streptococcus spp are most commonly isolated from the cat, however, other bacteria can also occur.

Pyometra can occur in any unspayed female, however, it is seen more commonly in older cats (over 5 years of age). Most cases of pyometra occur within 60 days of the female being in estrus.

What are the symptoms of pyometra in cats?

Pyometra usually appears 6 - 8 weeks after the queen goes out of heat. It is a life-threatening infection and requires immediate veterinary attention. Pyometra may come on quickly, or take several months to fully develop. Cats who have repeated heat cycles without being bred are at greater risk of developing pyometra.

There are two types of pyometra, open and closed.

  • Open pyometra: The cervix is open, and pus drains out of the vagina. This is often cream, pink or brown in colour, and has an offensive odour.

  • Closed pyometra: As the uterus is closed, pus is unable to drain from the vagina and therefore collects in the uterus.  


It is important to note that all cases of pyometra are medical emergencies, but closed pyometra is far more dangerous and life threatening. Both forms of pyometra require immediate veterinary attention. Pyometra can lead to organ damage and septicaemia.

As well as the possible discharge from the vagina, your cat may display some or all of the below symptoms:

How is pyometra diagnosed?

Your veterinarian will perform a physical examination of your cat and ask for a medical history such as when her last heat cycle was. He may observe the discharge of pus from the vagina, and be able to feel the enlarged uterus. This can be confirmed by ultrasound or x-ray

How is pyometra treated?

  • If the queen is not required for breeding purposes then an ovariohysterectomy (desexing/spaying) is the best option.

  • Antibiotics to control the infection.

  • IV fluids to treat dehydration.

  • If the cat is required for breeding, prostaglandin treatment will be used. This causes contraction of the uterus and the cervix to relax, which assists in evacuation of the pus. There may be side effects from the prostaglandin such as vomiting, diarrhoea, restlessness, panting, shock.

  • The pus may be cultured, and the queen will be placed on the appropriate antibiotics to treat the infection.

  • There is a chance that treatment will not be successful, and for pyometra to reoccur in cats treated for pyometra but not spayed.