Pyometra is a life-threatening infection of the uterus.
Pyometra only occurs in intact (not spayed) female dogs.
By 9 years of age two-thirds of bitches have changes to their uterine lining that allow for pyometra to develop.
Pyometra can lead to sepsis (bacteria in bloodstream), kidney failure, and liver failure.
Treatment of pyometra is surgical ovariohysterectomy (spay).
However, the surgery is much more difficult, risky, and costly compared to spaying early in life.