Pyometra is an infection of the uterus. It occurs frequently in older, non-desexed (entire) bitches and occasionally queens (entire cats). Pyometra is a serious condition and if left untreated can result in the death of your pet. As a result of the infection the bacteria absorb into the blood stream causing septicaemia and kidney problems.

Pyometra occurs usually 1-12 weeks after the dog or cat was on heat. With each cycle the uterus prepares for pregnancy and the lining gets thicker and produces more fluid. These changes occur under the influence of oestrogen. Once oestrogen levels fall down, progesterone (pregnancy hormone) starts being produced even if the dog/cat is not pregnant. Progesterone increases the chances of the uterus being infected and bacteria move from the vagina through the cervix inside the uterus.

Once infected the cervix may close and stay shut which causes “closed” pyometra that is more dangerous and harder to diagnose because no pus is seen draining out of the vagina. Sometimes the cervix opens and this is called “open” pyometra. It is easily diagnosed since the pus drains freely out of the vagina.

Who gets it?

Female entire dogs/cats develop pyometra and are usually 6 years and older. The great majority have never had a litter. Some animals may develop pyometra as a result of oestrogen use in order to treat other problems e.g. mismating.


Most animals with closed pyometra get very sick. High temperature, “brick red” mucus membranes, enlarged abdomen, increased water consumption/urination and lack of appetite are the most common symptoms.

If the dog/cat presents with “open “ pyometra they are usually not very sick and apart from pus draining from the vagina there may be no other signs.

It is important to note that the discharge can also be bloody.


There are different treatments available. Medical treatment exists but it often fails or may end up with complications. Antibiotics for 3 weeks can be given to animals with early pyometra if the animal shows no other major abnormalities at the time of the clinical xam. Valuable breeding stock can be treated with medications that increase the contractions of the uterus and help evacuate pus from it. However, since the uterus is fragile, it may rupture and complicate the treatment further and fertility could be affected.

The great majority of animals end up in surgery (ovariohysterectomy) and the uterus is removed with its contents. Since most of animals are very sick, extensive postoperative treatment is required and it consists of fluids, bloods, broad spectrum antibiotics and intensive care. Pyometra surgery is often challenging and is almost never simple.

Prognosis with prompt treatment is good to excellent.


Pyometra does not occur in desexed female dogs or cats so desexing is the best way of preventing it from happening. If you decided to use the bitch/queen for breeding do so because you may end up with another problem on your hands.

Desexing does not change your pet’s behaviour significantly and can save its life one day.

If you have any questions, please contact your local Vets4Pets practice.

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