"Pyometra" is a term that literally means "pus in the uterus". As a small animal veterinarian, I have treated many dogs with this condition. All female mammals are susceptible, of course, but in my experience, it is more common in dogs than cin ats.
A uterine infection generally becomes apparent within three weeks of a dog's heat cycle or, less commonly, up to three weeks after whelping (giving birth) or having a false pregnancy. At first, your dog may just seem a little 'off': not as playful, picking at her food, sleeping more than usual. Since this is an infection, most dogs develop a fever, but this can be difficult to detect if you are not actually taking your dog's temperature. A dry nose does not always indicate fever, and is not always present with a fever. However, because of the fever and the effects of the infection on the kidneys, dogs begin to drink excessive amounts of water and generally produce large amounts of very dilute, almost colorless urine.
In an 'open' pyometra, the dog's cervix is open, allowing pus (often tinged with blood) to drain from the uterus. You may see or smell this yellowish-brown discharge as it exits the vagina, but I have diagnosed dogs who were so fastidious that their owners never discovered the discharge.
With a 'closed' pyometra, the cervix is closed. Pus cannot be expelled, and the uterus swells. A closed pyometra is more dangerous than an open pyo. Bacteria and the toxins they produce are trapped in the body. Toxins and other products of the infection can damage the kidneys. The bacteria themselves can also enter the bloodstream, resulting in sepsis, toxemia, and death. The engorged uterus can also rupture, releasing pus, bacteria, and toxins into the abdominal cavity. This is nearly always fatal, without extreme intervention by a veterinary surgeon.
Diagnosis of pyometra is generally straight forward. A history of a recent heat cycle, false pregnancy, or delivering pups combined with increased thirst, poor appetite, and decresed energy level raise red flags. The distended uterus can often be felt on a physical exam, and if the cervix is open, discharge will be found, especially after gentle palpation of the uterus. A vaginal swab may reveal microscopic amounts of bacteria-laden white blood cells (pus), even in a closed pyometra. An x-ray or ultrasound may be obtained, partly to confirm the diagnosis prior to surgery, but also to assess the amount of uterine distension and look for signs of complicating factors, such as cancer. In an older female, pyometra can often be caused by ovarian cancer. It may be wise to obtain chest x-rays, just to make sure there is no indication of cancer or severe heart disease before going to surgery. Bloodwork is also useful. A red blood cell count needs to be obtained to check for signs of anemia that may require a blood transfusion. Platelet counts are needed to insure that the there will be no concerns with uncontrollable hemorrhaging. Red blood cell morphology (shape) should be evaluated for signs of disseminated intravascular coagulation (DIC), which can be fatal. If there is an open pyometra, and the dog is a valuable breeding animal, a white blood cell count is very important for determining whether or not it is safe to try to avoid surgery. An organ profile is also obtained to check for signs of kidney or liver damage.
In most cases, the best treatment for pyometra is surgical removal of the uterus and ovaries, along with intravaneous fluid therapy, intravaneous antibiotics (at least for the first 24 hours, after which oral ones may be given), and pain medications. Antibiotics are best chosen based on the results of culture and sensitivity testing (sending a sample of the bacteria to a laboratory, where it is grown and tested against various antibiotics). A combination of broad spectrum antibiotics is administered while results are obtained. Recovery from surgery following a pyometra is no different than recovery from a healthy spay (ovariohysterectomy), provided the uterus did not rupture and good surgical technique was used. If the kidneys and liver are healthy, there was no cancer present, the bacteria did not enter the bloodstream, there was no DIC, the correct antibiotics were chosen, and the uterus did not rupture, the dog could be eating and drinking normally within three days of surgery.
If the dog is a valuable breeding animal, or the owners simply cannot afford surgery, and there is an open cervix, medical treatment alone may be attempted. Ideally, a vaginal swab would be collected for antibiotic susceptibility testing. In the meantime, broad spectrum antibiotics, especially antibiotics that are taken up by white blood cells (therefore carried right to the source of infection), are the best choice. There is some controversy regarding the use of prostaglandins to keep the cervix open; I would suggest that they be used sparingly, if at all, and may only be necessary for the first three days, after which time (assuming the antibiotics are effective), there should be minimal discharge. Massaging the uterus to help expell pus may be attempted by a veterinarian, but is not recommended as a therapy to continue at home, because the infected tissue is delicate, and could easily rupture. Antibiotic therapy may be necessary for four to six weeks, depending on the type of bacteria present and severity of the infection. This can become quite costly.
Medical treatment for a closed pyometra is not recommended. The pus, loaded with bacteria and toxins, cannot escape the body, and has to be absorbed into the bloodstream in order to be removed. Furthermore, antibiotics cannot reach high enough concentrations within the fluid-filled uterus to kill enough bacteria. A closed pyometra will lead to sepsis, kidney failure, DIC, or uterine rupture, all of which result in death.
Uterine infection can occur any time that the cervix has been open, a normal occurance with the heat cycle or giving birth. It is more likely to occur when there is a hormonal abnormality, such as an ovarian cyst or ovarian tumors. It can occur at any age, but is much more common in older dogs that are experiencing irregular heat cycles. The most effective way to prevent uterine infection (as well as mammary cancer and unwanted pregnancies) is to spay (remove the uterus and ovaries) female dogs before their first heat cycle. As far as we know, dogs do not experience the physical and psychological side effects that human females do following this procedure. Most young dogs are back to normal, running around and acting pain-free, within three days of surgery-despite veternarians' warnings to keep surgery patients quiet for two weeks! It is much safer, and better for the dog over-all, to have the uterus removed when it is healthy, as opposed to waiting until removal becomes a surgical emergency.