Pyometra: A Nasty but Preventable Disease

Deciding not to spay a female dog or cat can have serious consequences. One serious condition is pyometra, and it can be life-threatening.

Spay females to prevent pyometra. By: paulcarless
Spay females to prevent pyometra. By: paulcarless

We recently performed surgery on a sweet little dog named Molly* who had pyometra, a severe condition where the uterus fills up with pus in a non-spayed female.

According to VCA Animal Hospitals, pyometra can present as a secondary infection when hormonal changes occur.

One of the contributing factors is a heat cycle. White blood cells, which fight against infection, are not present in the uterus so the sperm can survive.


Without a viable pregnancy, the walls of the uterus can thicken over several heat cycles. Cysts can form, and fluid (pus) can be released. That is an ideal environment for bacteria.

Symptoms of Pyometra in a Dog

Her human, Mary*, had noticed the following signs at home:

  • Weakness
  • Vomiting
  • Refusal to eat
  • Excessive drinking/thirst
  • Excessive urination
  • Fever

Mary had also noticed a reddish, foul-smelling discharge from Molly’s genitals.


Molly’s last heat was 6 weeks ago.

Blood work showed high kidney values, a low red blood cell count (anemia) and a high white blood cell count typical of an infection.

All these findings are suggestive of pyometra. At the local emergency clinic, X-rays, then an ultrasound, confirmed a pus-filled uterus.


Molly was not the greatest candidate for anesthesia or surgery. Her kidney values were higher than normal based on blood work, a sign of kidney disease — likely because of the pyometra.


But Mary didn’t really have a choice. The main risks of waiting and delaying surgery include shock, rupture of the uterus in the belly (often a death sentence), kidney failure and spreading of the infection to the bloodstream (a condition called sepsis).

Pyometra is a true surgical emergency. Antibiotics and IV fluids were started immediately. Molly was anesthetized and had surgery to remove her ovaries and uterus (ovario-hysterectomy), which was indeed grossly distended with pus. A culture (a sterile swab) was done during the surgery. It revealed that E. coli was growing in Molly’s uterus. It sometimes can also be a simple staph infection.

Pyometra is a complex disease involving hormones and bacteria. If bacteria arrive in the uterus at a certain time during the female cycle, an infection will develop, start a complicated disease process and can culminate in death. These bacteria are most often present in the dog’s normal intestine, vagina or bladder.

In the video below, veterinarian “Doc Pawsitive” discusses a recent surgery on a dog with pyometra. (Warning: Content that may be considered graphic begins at 3:20, when a dog’s removed uterus is examined.)

Up to 25 percent of unspayed female dogs can develop this disease. That is an incredibly high risk — and totally preventable. Some dogs who received hormones (estrogens, progesterone) may have an increased risk.

Cats can be affected as well, although less commonly than dogs. An important difference is that whereas dogs can have pyometra four to eight weeks after a heat cycle, cats can get it within one to four weeks.

Importantly, it can happen in pets of any age, from puppies to geriatrics, as long as they’re not spayed.

In essence, we performed a fancy spay on Molly, except that it was done on a poor anesthesia candidate, a very sick dog, with much more discomfort and at a much greater cost to Mary.

Kismet had surgery for pyometra. By: MeowMixx1980
Kismet had surgery for pyometra. By: MeowMixx1980


Few diseases are completely preventable. Pyometra is one condition that is easy to prevent entirely. Had Molly been spayed as a puppy, she would never have had this life-threatening condition.

For your dog’s or your cat’s benefit, and yours, please spay her as young as possible. Your vet can recommend the ideal time. It should definitely be done before the first heat.

More and more vets recommend spaying (and neutering) dogs and cats well before puberty. Interestingly, spaying before the first heat cycle also virtually eliminates the risk of mammary (or breast) tumors.

As Doc Pawsitive stated in the above video, “Getting your dog spayed is not birth control. It is health control.”

*Names have been changed to protect the privacy of the client.

vet-cross60pThis pet health content was written by a veterinarian, Dr. Phil Zeltzman, DVM, DACVS, CVJ. It was reviewed for accuracy by Dr. Pippa Elliott, BVMS, MRCVS, and was last updated Dec. 17, 2018.

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