What Are the Signs of Pyometra in Dogs and How Is It Treated?

If you’ve noticed your unspayed female dog acting lethargic, drinking more water than usual, or showing unusual discharge, you’re right to be concerned. Pyometra is a serious bacterial infection of the uterus that can turn life-threatening fast, and it’s one of the most common emergencies vets see in unspayed female dogs and cats. The good news: caught early and treated quickly, most pets recover well.

Here’s what you need to know, from symptoms to treatment, so you can act fast if you need to.

What is pyometra?

Pyometra is a bacterial infection of the uterus that causes it to fill with pus. It almost exclusively affects unspayed females, and it tends to develop in the weeks following a heat cycle, when hormonal changes make the uterus especially vulnerable to infection.

Here’s what’s happening inside: after each heat cycle, rising progesterone levels (the hormone that prepares the uterus for pregnancy) cause the uterine lining to thicken. Over time, this repeated thickening can lead to a condition called endometrial hyperplasia, which basically means the uterine lining has become abnormally thick and cyst-filled. That environment is ideal for bacteria to move in, multiply, and cause a full-blown infection. The uterus fills with pus, swells, and if it’s not treated quickly, the infection can spread to the bloodstream, which becomes life-threatening.

It can happen in both dogs and cats, though it’s diagnosed more frequently in dogs. Middle-aged to older unspayed females are most at risk, but it can affect younger animals too.

Open vs. closed pyometra: what’s the difference?

There are two forms of pyometra, and the distinction matters because one is easier to spot than the other.

Open pyometra

In open pyometra, the cervix (the opening between the uterus and the vagina) stays open, which means the infected fluid can drain out. You’ll often see a discharge that ranges from pinkish to yellowish-brown or greenish, and it may smell foul. While this is alarming to see, it’s actually the easier form to catch early because there’s a visible sign.

Closed pyometra

In closed pyometra, the cervix is sealed shut. The pus has nowhere to go, so it builds up inside the uterus. Because there’s no external discharge, the signs are more subtle and easier to miss until the infection becomes severe. The uterus can become dramatically enlarged, and the risk of it rupturing is real. This form tends to be more dangerous and progress faster.

Stump pyometra

There’s also a less common form called stump pyometra, which can occur in dogs that have been spayed but had a small portion of the uterus left behind during surgery. That remaining tissue can still become infected, especially if any ovarian tissue was also left. It’s rare, but worth knowing about if your dog has been spayed and is showing symptoms.

Symptoms of pyometra in dogs and cats

Pyometra symptoms can look like a lot of other conditions, which is part of what makes it tricky. But there are some patterns to watch for, especially in unspayed females in the two to eight weeks after a heat cycle.

Early signs of pyometra in dogs and cats include:

• Lethargy or unusual tiredness
• Decreased appetite
• Increased thirst and urination
• Vomiting or diarrhea
• A distended or swollen abdomen (especially in closed pyometra)
• Vaginal discharge that may be cloudy, bloody, or yellowish-green (in open pyometra)
• Excessive licking at the vulva
• Fever (though not always present)

If your dog or cat is showing any combination of these signs, and especially if she’s unspayed and recently finished a heat cycle, don’t wait to see if she improves. Call your vet or an emergency animal hospital right away.

How vets diagnose pyometra

Your vet will start with a physical exam and take your pet’s history, including when her last heat cycle was. From there, they’ll typically run a combination of tests to confirm the diagnosis and assess how sick she is.

• Blood work: A complete blood count and chemistry panel to check for signs of infection, kidney function, and overall organ health. Pyometra can affect the kidneys, so this matters for treatment planning.
• Urinalysis: A urine test to check kidney function and rule out other conditions.
• X-rays or ultrasound: Imaging lets the vet actually see the uterus. An enlarged, fluid-filled uterus on an ultrasound is a strong indicator of pyometra. Ultrasound is particularly useful because it can distinguish pyometra from pregnancy.

In most cases, a vet can make a confident diagnosis fairly quickly with these tools, which is important since time is a factor.

Pyometra treatment: what to expect

The standard and most effective treatment for pyometra is emergency spay surgery, called an ovariohysterectomy. This means surgically removing the uterus and ovaries entirely, which eliminates the infection at its source. When performed before the infection spreads to the bloodstream, the success rate is high.

Before and after surgery, your vet will likely recommend:

• Intravenous (IV) fluids to stabilize your pet and support kidney function
• Antibiotics to fight the bacterial infection
• Pain management during recovery
• Hospitalization for monitoring, usually one to several days depending on how severe the infection was

What about medical management?

In some cases, vets may discuss a non-surgical option using hormone-based medications to cause the cervix to open and the uterus to contract and expel the infection. This approach is generally only considered for younger dogs whose owners want to preserve breeding potential, and it comes with significant limitations: it’s less reliable, requires close monitoring, carries a higher risk of recurrence, and isn’t appropriate for closed pyometra or severely ill animals. Your vet will tell you honestly whether it’s a viable option for your specific pet.

How long does pyometra take to become life-threatening?

This is one of the most urgent questions pet owners ask. The honest answer: it depends on the form. Closed pyometra can deteriorate rapidly, sometimes within days, because the pus has nowhere to go and the uterus can rupture. Open pyometra may progress more slowly, but it’s still an emergency. If you suspect pyometra, same-day veterinary care is the goal. Don’t wait for a regular appointment.

Pyometra surgery cost

Emergency pyometra treatment is one of the more expensive veterinary situations you can face. The total cost typically includes diagnostics, surgery, anesthesia, hospitalization, IV fluids, and medications, and it can range from roughly $1,500 to $5,000 or more depending on your location, the severity of the infection, and how long your pet needs to be hospitalized. If complications arise, such as kidney damage or sepsis (a severe, body-wide response to infection), costs can climb higher.

That’s a significant bill to face in an emergency. Having pet insurance in place before any symptoms appear can make a real difference.

Does pet insurance cover pyometra?

A Lemonade Pet policy may be able to cover diagnostics and treatment for pyometra, including surgery and hospitalization, as long as the condition isn’t pre-existing and symptoms first appear after your 14-day illness waiting period. Coverage can also depend on whether you’ve followed your vet’s care recommendations, since declining a spay that your vet specifically and repeatedly recommended can impact a claim.

The most reliable way to prevent pyometra from occurring in the first place is spaying. One of Lemonade Pet’s preventative care add-ons can help cover a portion of your dog’s spay procedure, along with other essentials like wellness exams and vaccines. It’s one of those situations where preventing the problem altogether is both the kindest thing for your dog and the smartest financial move.

Prevention: the simplest answer is spaying

Spaying your dog or cat before her first heat cycle essentially eliminates the risk of pyometra entirely, since there’s no uterus left to become infected. It also reduces the risk of mammary tumors (breast cancer in dogs and cats) and eliminates the risk of other uterine diseases.

If your pet is older and hasn’t been spayed, it’s not too late to talk to your vet about whether elective spaying makes sense. The risk of pyometra increases with each heat cycle, so it’s a conversation worth having.

Before we go

Pyometra is scary, but it’s also very treatable when caught quickly. If your unspayed female dog or cat is showing any of the warning signs, especially in the weeks after a heat cycle, get to a vet the same day. Fast action is what makes the difference between a full recovery and a crisis. And if you haven’t already looked into pet insurance for your unspayed pet, now is the right time, before anything happens, so you’re covered if it does.

Frequently Asked Questions

A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC.  The statements do not apply to policies underwritten by other carriers.