Pyometra in Dogs: Signs, Why It's Urgent and Treatment

What pyometra is

After every heat, a female dog has weeks of high progesterone, a hormone that prepares the uterus for pregnancy by thickening its lining. VCA explains that over repeated cycles the lining can become cystic and fill with fluid, and the uterus loses some of its ability to contract and empty. Bacteria that entered while the cervix was open during heat then multiply in that fluid, and the uterus fills with pus.

The Merck Veterinary Manual notes pyometra is mostly seen in unspayed dogs over five years old, usually four to six weeks after a heat, though VCA reports it can appear anywhere from two to sixteen weeks after. Hormone medicines containing estrogen or progesterone can also trigger it. Spayed dogs, whose uterus has been removed, essentially cannot develop it.

Signs of pyometra: open and closed

Vets describe two forms. In open pyometra, the cervix stays partly open, and pus drains out as a creamy, yellow, green, red or brown discharge from the vulva, often with a strong smell. You may notice your dog licking her rear more, stains on her bedding, or flies around her tail. Because the infection can drain, a dog with open pyometra may seem only mildly unwell at first.

In closed pyometra, the cervix is shut, so there is no discharge and pus builds up inside. These dogs become very sick quickly. Signs of both forms include lethargy, a poor appetite, drinking and urinating much more than usual, vomiting, diarrhea, fever and, with a closed cervix, a swollen or tender belly. Some dogs pant, shake or seem restless.

When to call your vet today

Call your vet the same day if your unspayed female dog has any vaginal discharge outside of her normal heat, or if she is drinking or peeing more, less interested in food, or quieter than usual in the weeks after a heat. Tell the clinic when her last heat ended. Do not wait to see whether she improves; pyometra can worsen within hours.

It is also worth calling if a female dog was given hormone medicines, or if a dog was thought to have been spayed but shows heat-like signs, since a small piece of ovary left behind can occasionally cause problems later.

When it's an emergency

Go to your vet or the nearest emergency vet immediately if your unspayed dog is vomiting, very lethargic or weak, has a swollen belly, pale or dark red gums, a fast heart rate or rapid breathing, or collapses, whether or not there is discharge. These are signs of closed pyometra or of infection spreading through the body.

VCA warns that bacterial toxins affect the kidneys, and that a pus-filled uterus can rupture and spill infection into the abdomen, which is often fatal. Merck notes pyometra can progress rapidly to shock and death. Call ahead so the team can prepare for possible emergency surgery.

What you can safely do at home

The only safe home step is getting her to a vet quickly. While you arrange it, keep her calm and comfortable, offer water, and note when her last heat started and ended, when signs began, and whether she has had any medicine. If there is discharge, a photo or a stained tissue helps your vet.

Do not give antibiotics left over from another illness, human pain relievers or herbal remedies. Antibiotics alone do not cure pyometra, and some human medicines are dangerous to dogs and can make surgery riskier. Do not delay care because she is still eating; some dogs with open pyometra keep their appetite for a while.

A dog diaper can keep discharge off furniture on the way to the clinic, but note how much discharge there is first so you can tell the vet.

What the vet will likely check

Your vet will examine your dog and look at any discharge. Blood tests often show a very high white blood cell count and can show how the kidneys are coping, and urine may be unusually dilute. An ultrasound or X-ray confirms whether the uterus is enlarged and fluid-filled, and helps tell pyometra apart from pregnancy.

Treatment in most cases is emergency surgery to remove the infected uterus and ovaries, along with intravenous fluids, antibiotics and pain relief. Surgery in a sick dog carries more risk than a routine spay, so prompt treatment improves the odds. Medical treatment with hormone injections is occasionally considered for a young, stable breeding dog, but VCA describes it as slower and less reliable, and Merck notes pyometra tends to come back afterward.

Prevention

Spaying removes the uterus and therefore prevents pyometra. If you are not planning to breed your dog, talk to your vet about the right age and timing to spay. If she is a breeding dog, Merck advises spaying once her breeding life is over, because the risk rises with age and with each cycle.

Until then, keep a calendar of her heats and watch closely for any discharge, extra thirst, reduced appetite or tiredness in the two months after each one. Avoid hormone medicines unless your vet has prescribed them.

This page is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your pet.