The Canine Ledger

Pyometra: The Emergency in Unspayed Females

Pyometra is a womb infection that can kill an unspayed female dog. The signs, who is at risk, how long after a season it strikes, and the treatment options.

Written by thecanineledger

If your unspayed female dog is unwell in the weeks after a season, especially if she is off her food, drinking more, lethargic, vomiting, or has a discharge from her vulva: phone your vet today and say you are worried about pyometra. If she is collapsed, very weak or has pale gums, go to the nearest open vet now. There may be no discharge at all.

In a study of more than 200,000 insured dogs in Sweden, on average “23-24% of the bitches in the databases will have experienced pyometra by 10 years of age” (Egenvall et al., Journal of Veterinary Internal Medicine 2001, abstract). In some breeds, it was more than half.

That is roughly one female in four. Few other emergencies are that predictable, or that easy to miss.

While most owners of unspayed females know about seasons and accidental matings, far fewer know that the weeks after a season carry a risk of a serious infection. This page covers what pyometra is, the signs, which dogs are most at risk, and what the treatment options are.

1. What it is

Pyometra is an infection of the womb (uterus), which fills with pus. The American College of Veterinary Surgeons (ACVS) explains that the female hormone cycle changes the uterus so it is ready for a pregnancy. “If bacteria are introduced into the uterus at a certain time during the cycle, hormonal regulation of the uterus allows the infection to start and become life-threatening” (ACVS, Pyometra). The most common bacterium is E. coli.

The timing is the clue. A 2026 review explains that “Clinical signs typically occur 6–10 weeks after heat in bitches” (Goericke-Pesch, Reproduction in Domestic Animals 2026). If your female is unwell a month or two after a season, tell the vet when her last season was.

It is an emergency because of what it does to the rest of the body. The ACVS: “Because the infection can be so severe, the signs your pet may show are not limited to the genital tract.” The infection can spread into the blood. The same review describes pyometra as potentially “life‐threatening due to septicaemia”, meaning blood poisoning.

2. The signs

The ACVS lists the most common signs in dogs and cats:

  • lethargy and depression
  • not eating
  • drinking much more than usual
  • passing much more urine
  • pale gums
  • a bloody discharge from the vulva

Less often, it lists vomiting, diarrhoea, weight loss, a swollen belly, and inflamed eyes.

No discharge doesn’t mean no pyometra. The ACVS warns that “Many dogs and cats will have a closed cervix and therefore the obvious sign of bloody vaginal discharge may not be present.” This “closed” pyometra is the one owners miss, because the pus stays inside.

The rule the surgeons give vets applies to owners too. The ACVS: “Pyometra should be considered in any intact female dog that is sick.” Intact means not spayed.

Our note: The ACVS calls pyometra “a medical emergency”. If you’re unsure, go now.

→ Emergency Signs in Dogs: When to Go Now, Not Tomorrow

3. Which dogs are at risk

Unspayed females, usually in middle age. A 2023 review notes that “A higher occurrence of pyometra is seen in animals around seven years of age”, though it has been described from three months to 20 years (Xavier et al., Animals 2023).

Some breeds carry more risk. In the Swedish insurance study, the share of females affected by 10 years of age “ranged between 10 and 54%” across breeds. Risk was higher in:

  • Rough Collies
  • Rottweilers
  • Cavalier King Charles Spaniels
  • Golden Retrievers
  • Bernese Mountain Dogs
  • English Cocker Spaniels

Read the Swedish figures with care. They come from insured female dogs in Sweden in 1995 and 1996. Where most females are spayed young, owners will see far fewer cases. For an unspayed female, the figures still describe the risk she carries.

Spayed dogs are not entirely safe. The ACVS explains that “Most dogs and cats that are spayed early in life will not develop pyometra”, but a “uterine stump pyometra” can occur when some ovarian tissue was left behind, or after hormone treatment.

Our note: The only lifetime risk figures we found come from a 2001 Swedish study, read as an abstract.

4. Treatment

Surgery is the usual treatment. The ACVS: “Pyometra is a medical emergency that requires rapid intervention to prevent overwhelming infection and death.” It describes stabilising the dog first, with fluids and other support, and then “ovariohysterectomy (spay) is the therapy of choice.” The 2026 review agrees that “Surgical ovariohysterectomy remains the treatment of choice”.

Most dogs survive surgery. The ACVS says survival “can be as high as 80–100% if abdominal contamination is avoided and the systemic infection is treated and responds appropriately.” In a 2026 study of 470 dogs operated on at several hospitals, 18 (3.8%) died before going home, and 97.8% of those discharged were alive two weeks later (Langfitt et al., Frontiers in Veterinary Science 2026, abstract). Survival was better in younger dogs, and in dogs without signs of kidney trouble, high potassium or low blood sugar before surgery.

“Emergency” means get to the vet. It doesn’t always mean surgery that minute. A 2026 study of 137 dogs at three referral hospitals found no difference in surgery time, anaesthetic time or hospital stay whether the operation happened quickly or after a longer period of stabilisation. The authors concluded that “Immediate surgical intervention for patients with pyometra may not be superior to delayed surgical intervention” (Durocher et al., Journal of the American Veterinary Medical Association 2026, abstract). This is about the timing of surgery once a dog is in a vet’s hands. It is not a reason to wait at home.

Our note: The 2026 timing study is no reason to delay getting your dog to a vet.

→ How Risky Is Anaesthesia for My Dog?

5. Medical treatment, for breeding females

For a female who will be bred again, some vets offer medical treatment with hormone drugs instead of surgery. The ACVS says this needs “very special case selection meeting certain criteria”. It warns that the effect takes several days to appear, and that “Dogs and cats are susceptible to developing pyometra again after medical treatment and should have an ovariohysterectomy performed when their breeding purposes are finished.”

The results can be good in selected dogs. In a 2019 study of 174 females given medical treatment, the authors report that “Treatment was 100% successful”, that 8.62% relapsed, and a pregnancy rate afterwards of 92.14% (Melandri et al., Journal of Veterinary Science 2019). These dogs were selected for medical treatment, so the figures will not apply to every dog.

We are not naming drugs or doses. Medical treatment is a specialist decision, made by your vet with your dog in front of them.

Our note: The Melandri study reports 100% success, but in selected cases.

6. Preventing it

Spaying early in life prevents most pyometra. That is a real benefit, and it is one factor in the decision about whether and when to spay. It is not the only factor. The breed studies on spay timing point in different directions for different conditions, and we cover them separately.

→ When to Spay or Neuter: What the Breed Studies Show, and What They Don’t

If you keep your female entire, know the timing. Note the date of every season, and treat any illness in the two months after one as possible pyometra until a vet says otherwise.

7. What we could not verify

Commonly saidWhat we found
“Pyometra always causes a discharge”Contradicted. The ACVS says many dogs have a closed cervix and no obvious discharge.
“Only old dogs get pyometra”Not only. It is most common around seven, but has been described from three months of age.
“Spayed dogs can’t get pyometra”Not quite. A stump pyometra can occur if ovarian tissue was left, or after hormone treatment.
“Antibiotics alone will cure it”Not what the sources say. The ACVS and the 2026 review describe surgery as the treatment of choice; the ACVS describes medical treatment as hormone injections with antibiotics, not antibiotics alone.
“A quarter of all female dogs get pyometra”That figure comes from Swedish insurance data from the 1990s, by age 10. Where most females are spayed young, it will be far lower.
How many dogs die of pyometra each yearWe found no population figure. Survival after surgery is high in the studies we read.

Sources

Always confirm with your vet before acting on anything on this page.