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What is it?

Pyometra, or "a Pyo", is an infection of a dog's uterus (womb). It is a severe and potentially fatal condition, and preventing it is one of the main reasons for spaying bitches.

What causes it?

In a normal, healthy bitch, after every season her uterus prepares to receive puppies (this is driven by the hormone progesterone), and whether or not she becomes pregnant, the uterine wall will thicken and secrete fluid. As she gets older, this becomes more and more pronounced - we call this Cystic Endometrial Hyperplasia. Once she's decided she isn't actually pregnant (about 2 months after her season), the lining thins down and the fluid is reabsorbed. However, if during this time bacteria can enter the uterus, this fluid is a perfect foodstuff for them, and they rapidly grow and multiply, causing disease. There are two types of Pyo - an Open Pyo (where the cervix remains open, so the pus can drain out of her vagina and vulva), and a Closed Pyo (where the cervix is closed so all the bacteria, pus and toxins are trapped inside). Although both are dangerous, a Closed Pyo is more likely to be fatal, and is harder to diagnose.

What dogs are at risk?

Any unspayed bitch - although it may be slightly more common in those who haven't had a litter (although it can happen to any bitch). It usually develops within 3 months of a season, and is more likely in older dogs. Overall, 23% of unspayed bitches can be expected to develop a Pyo by 10 years of age.

What are the symptoms?

A dog with an Open Pyo may just appear a little off colour, with a thick cream, yellow or greenish vaginal discharge. However, more often she will be displaying signs of systemic illness, typically increased thirst and urination, lethargy, and loss of appetite. A Closed Pyo is more dangerous, as there is no discharge to warn you of a problem. She will start out with these non-specific signs, but then rapidly deteriorate and start vomiting, her gums may change colour (to red or possibly pale grey), and her abdomen may seem to swell. Ultimately, she will collapse, go into shock and die.

How is it diagnosed?

Usually with an ultrasound scan to look at the uterus - a pus-filled, inflamed uterus is very obvious on ultrasound. Other possible tests include blood tests and a vaginal exam.

How can it be treated or managed?

The treatment of choice is ALWAYS surgical removal of the infected uterus, and this is the only effective treatment for Closed Pyos. In an Open Pyo, it may be possible to use hormones (to make the uterus shrink down and expel the infection) and antibiotics (to treat the bacteria) - however, although many dogs will apparently respond to this treatment, the Pyo will recur after the next season in over 80% of cases.

Can it be prevented?

Yes - by spaying. A neutered bitch cannot develop a true pyo.