What is Pyometra?

The word pyometra is derived from the Latin word “pyo” meaning pus and “metra” meaning uterus. A pyometra is an abscessed, pus filled infected uterus. During this infection, toxins and bacteria leak across the uterine walls and into the bloodstream, causing life-threatening toxic effects. In some cases, the uterus dies, releasing large amounts of pus and dead tissue into the abdomen. Without treatment the infection will become fatal to the cat or dog. Prevention of this disease is one of the main reasons for routinely spaying female dogs and cats.


What Causes Pyometra?

With each heat cycle, the uterine lining engorges in preparation for pregnancy. Eventually, some tissue engorgement becomes excessive or persistent (a condition called cystic endometrial hyperplasia). This lush glandular tissue is ripe for infection (recall that while the inside of the uterus is sterile, the vagina below is loaded with bacteria). Bacteria ascend from the vagina and the uterus becomes infected and ultimately filled with pus. Hormonal effects on the uterine tissue accumulate with each heat cycle, which means pyometra is much more common in older females because they have experienced many hormonal cycles.


Diagnosing Pyometra

There are many indications of pyometra which help veterinarians diagnose this condition:

    • In most cases, older female dogs are predisposed to pyometra.
    • Typically, these females would have just finished a heat cycle, within 1-2 months prior to showing symptoms
    • The female will have a poor appetite and may be vomiting or drinking an excessive amount of water.
    • In the more usual “open pyometra,” the cervix is open and the purulent uterine contents are able to drip out so that a smelly vaginal discharge is usually apparent.
    • However, there is also a form called a closed pyometra where the cervix is closed. In these cases, there is no vaginal discharge and the clinical presentation is more difficult to diagnose. These patients also tend to be sicker than those with open pyometra due to retention of the toxic uterine contents as well as a longer disease course prior to diagnosis.
    • Blood work may be conducted which can show a pattern typical of widespread infection that is often helpful in narrowing down the diagnosis.
    • Radiographs may show a gigantic distended uterus, though sometimes this is not obvious and an ultrasound is needed to confirm the diagnosis.


Treatment of Pyometra

The usual treatment for pyometra is surgical removal of the uterus and ovaries. It is crucial that the infected uterine contents do not spill into the abdomen and that no excess bleeding occurs. The surgery is challenging, especially if the patient is toxic.

Generally, antibiotics are given at the time of surgery and may or may not be continued after the uterus is removed. Pain relievers are often needed post-operatively. A few days of hospitalisation are typically needed after the surgery is performed. It is especially important that the ovaries be removed to prevent future hormonal influence on any small stumps of uterus that might be left behind. If any portion of the ovary is left, the patient will continue to experience heat cycles and be vulnerable to recurrence.

While pyometra surgery amounts to the same end result as routine spaying, there is nothing routine about a pyometra spay. As noted, the surgery is challenging and the patient is in a life-threatening situation. For these reasons, the pyometra spay typically costs more than a routine spay.



Spaying represents the complete prevention for this condition. The importance of spaying cannot be over emphasised. Often an owner plans to breed a pet or is undecided, then time passes, and then they fear she is too old to be spayed. The female dog or cat can benefit from spaying at any age. It is important to note that pyometra is very likely to occur if a female is not spayed. Therefore, from a scientific point of view, any perceived risks of surgery are very much out-weighed by the risk of pyometra.


Feline Pyometra

Female cats may also fall victim to pyometra. In cats, the disease is just as serious and the treatment options are the same. There is an important difference for cats with pyometra however - female cats rarely appear sick until in very late stages of the disease. The classic creamy vaginal discharge is present and often the belly appears distended because of the size of the pus-filled uterus, but the cat herself is generally eating and grooming as if nothing much is going on. If the female cat is fastidious and cleans away the discharge, the pet owner may wrongly conclude that she is simply pregnant. Unfortunately, this lack of apparent illness leads to a delay in diagnosis and this delay can become fatal in an apparent quicker timeframe.