As I mentioned in a post a couple of weeks ago, there are many pro's to spaying your pet. Not having the risk of pyometra is quite possibly the biggest, aside from an unplanned litter. (This isn't Teen Mom. What lies ahead for owners of pregnant pups are lots of vet bills, and no reality tv shows). It is a potentially fatal disease akin to appendictis in humans.
Pyometra is an infection of the uterus, and can occur in humans (much less common) cats, and other small mammals. It can occur in intact females of any age, but is more common the older the pet.
Though mainly caused by hormonal changes inside the uterus that create an ideal growth environment for bacteria, synthetic hormones can also increase a dog's risk of developing infection. Because the cervix opens during the heat cycle, bacteria normally found in the vagina can enter the uterus more easily. When the cervix closes, bacteria is trapped inside and left to fester without a method of escape. The infection worsens over time, and pyometra is usually seen 2-8 weeks post estrus.
Signs include purulent discharge from the vagina, fever, lethargy, and anorexia, though symptoms may vary depending upon if the cervix is closed or not. Because the toxins released by bacteria hinder the kidney's ability to retain fluid, many dogs drink more to accomodate for the increased urine production.
Pyometra is diagnosed through veterinary examination and a variety of tests not limited to radiographs, urine specific gravity, and white blood cell counts.
The primary treatment is removal of the infected uterus and ovaries through surgery, (an ovariohysterectomy for those of you who read the post a couple of weeks back.) Surgery is often far more complicated in pyometra cases, as the pet is usually very ill and requires hospitalization for IV fluids and antibiotics, but generally has a rapid recovery and minimal risk of recurrence.
If left untreated, the uterus can rupture leading to peritonitis and rapid death.
Given all the congenital health issues that can arise for pets, why wouldn't you eliminate one more hazard completely if you could by spaying your pet? It's one of many benefits, and cheaper monetarily and emotionally to spay your pet while she is not suffering from a life threatening illness.