Pyometra is an overwhelming infection of the uterus. It is considered a severe condition and requires immediate veterinary attention. This condition occurs in adult unspayed female dogs and cats. It can happen to any dog or cat who has reached sexual maturity, but it is most commonly found in middle-aged to older dogs.
Pyometra occurs as a consequence of the hormonal changes in a female’s reproductive tract. During the heat cycle, white blood cells (which protect the body from infection) are inhibited by the body from entering the uterus to allow the sperm to safely enter the female’s reproductive tract without being attacked by these protector cells. The female’s hormone levels remain elevated for up to 8 weeks after a heat as preparation for pregnancy and fetal development. This high hormonal level causes a thickening of the lining of the uterus. If pregnancy does not occur, the uterus lining continues to increase in thickness and cysts can form in the tissues of the cervix. The thickened uterus secretes fluids that create a nutrient-rich environment for bacteria to grow in. The elevated hormonal level limits the ability of the uterus to expel the accumulation of fluids and bacteria. This combination of critical factors creates pyometra, typically 2 to 8 weeks after the last heat cycle.
Bacteria enter the uterus through the cervix. The cervix stays tightly closed except during the heat cycle. During the heat cycle, the cervix relaxes to allow sperm to enter the uterus. Bacteria take root in the ideal environment created by the heat cycle and replicates rapidly causing the womb to fill with large volumes of bacteria-filled fluid. The bacteria in the uterus produces toxins that can enter the bloodstream and cause systemic illness.
Two Types of Pyometra
In an open pyometra, the cervix remains slightly open which allows some of the fluid to drain out of the uterus. Dogs with open pyometra will have an abnormal, heavy pus-like discharge from their vulva. They may also have a fever, poor appetite, and lethargy.
In a closed pyometra, the cervix closes, and the pus that forms is not able to drain from the uterus. The discharge will continue to build, and there may be abdominal distention. Because none of the pus can drain in a closed pyometra, dogs with this form get very ill very quickly and exhibit severe clinical signs of lethargy, no appetite, fever, depression. The toxins released by the bacteria affect the kidney’s ability to retain fluid resulting in increased urine production. As a result, dogs with pyometra (both open and closed forms) drink much more water to compensate for the increased urination.
The best way to treat pyometra is to surgically remove the infected uterus and ovaries (an ovariohysterectomy – aka “spay”). Most dogs diagnosed with this disease are quite ill when they are presented at the veterinary clinic. So, although the treatment is essential to spay the female, the procedure is much more complicated than a routine spay. Frequently, the patient is so ill that stabilization is required with hospitalization, intravenous fluids and intravenous antibiotics before surgery can be done. Antibiotic therapy for several days (or weeks) after the procedure is also required. The chance of a successful resolution without surgery is meagre. If the treatment is not done quickly, the toxic effects from the bacteria in the uterus will be fatal in most cases.
Pyometra is preventable by spaying your dog while she is still a puppy to young adult.
Written by Shanon Chase, RVT