Pyometra in cats is a serious uterine infection that affects intact (unspayed) females, and it can be life-threatening if it is not treated quickly. It is still fairly unknown to many owners of intact cats, which is exactly why the veterinary team needs to understand it well enough to explain it.
The point to remember: an intact female cat who goes quiet and stops eating in the weeks after a heat needs to see a veterinarian the same day, even if you have not seen any discharge. Spaying prevents pyometra, which is one reason a routine spay is about more than population control.
What is pyometra in cats?
Pyometra means a pus-filled uterus. It usually develops on top of a condition called cystic endometrial hyperplasia (CEH), where the uterine lining thickens, forms cysts, and secretes fluid that gives bacteria a good place to grow. For a broader overview that covers dogs as well, see our post on pyometra in dogs and cats.
The trigger is hormonal, and the feline cycle matters here. Cats mostly ovulate when they mate, but they can also ovulate on their own. If ovulation happens and the cat does not become pregnant, her body keeps producing progesterone for about 40 days. That phase after ovulation is called diestrus, and it is when most cases of pyometra start. (Our guide to how long a cat stays in heat explains the stages of the heat cycle.)
Progesterone works against the uterus in three ways during diestrus:
- It stimulates the uterine glands to secrete fluid, which bacteria can grow in.
- It suppresses the local immune response.
- It reduces the contractions of the uterine muscle, and the cervix may close, so the uterus cannot empty itself.
Pyometra can occur at any age, but the risk rises as cats get older, with a marked increase after about 7 years in Swedish insurance data. It is most often seen in middle-aged and older queens that have never had a litter. In that same Swedish data, some breeds, including the Sphynx, had a higher incidence. Signs most commonly appear within about 4 weeks of the start of a heat.
What are the symptoms of pyometra in cats?
The signs depend largely on whether the cervix stays open or closed.
Open pyometra. With the cervix open, pus can drain out of the vulva. Owners may notice discharge on the tail or the fur, or stains where the cat usually rests. In some cats with an open pyometra, the discharge is the only sign. Cats are fastidious groomers, though, so this classic discharge often goes unnoticed.
Closed pyometra. With the cervix closed, the pus has nowhere to go. Fluid builds up in the uterus and the belly may look swollen, sometimes enough that the owner notices the change in shape. These cats tend to become seriously ill quickly. Bacterial toxins can enter the circulation and lead to sepsis, and a distended uterus can rupture or leak pus into the abdomen, causing peritonitis (inflammation and infection of the abdominal lining).
In either form, the signs owners most often see at home are:
- Poor appetite or not eating
- Lethargy (being quiet, sleeping more, hiding)
- Vaginal discharge, if the cervix is open
- Vomiting
- Fever
- A swollen belly, more typical of a closed pyometra
Signs in cats are similar to those in dogs but usually less obvious. Drinking and urinating more, a well-known sign in dogs, is possible in cats but much less common. Some queens show only mild signs and normal-looking lab work, so pyometra in cats often goes undiagnosed until the cat is quite sick.
When to call your vet: if your intact female cat is off her food, unusually quiet, vomiting, has any vaginal discharge, or has a swollen belly, especially in the weeks after a heat, call your veterinarian the same day. An open pyometra may look milder than a closed one, but both are emergencies.
How is pyometra diagnosed?
Any intact female cat that is unwell, particularly with abdominal pain, should have pyometra on the list of possibilities. A detailed history matters because the signs can be subtle: when her last heat was, whether she was mated, and whether she has received any hormone treatment.
Discharge raises suspicion, but it does not confirm the diagnosis on its own. Your veterinarian will usually combine:
- A physical exam, including a check of the abdomen and the vulva.
- Abdominal ultrasound, the most useful test in cats. It shows a fluid-filled uterus and tells pyometra apart from pregnancy.
- X-rays (radiographs), which can show an enlarged uterus. They are suggestive but not definitive.
- Bloodwork and urinalysis. A complete blood count (CBC) often shows a high white blood cell count, but blood results in cats with pyometra can look surprisingly normal, so normal bloodwork does not rule it out. Chemistry and urinalysis help assess how sick she is overall.
- Vaginal cytology, a swab of the discharge examined under the microscope, when discharge is present.
How is pyometra in cats treated?
Surgery is the treatment of choice. That means an ovariohysterectomy, the same spay operation that removes the ovaries and uterus, performed as an emergency procedure. It removes the infection and the risk of it coming back.
Many cats arrive sick, so stabilization comes first: the veterinary team typically starts intravenous fluids and antibiotics before surgery. The cat is then hospitalized after surgery so she can be monitored for complications. When she goes home, your veterinarian will send any medication she needs and explain the recheck plan.
The outlook after surgery is generally good, especially when the cat is treated early. The American College of Veterinary Surgeons (ACVS) describes survival with surgery as high as 80-100% when the infection is controlled and the abdomen is not contaminated, usually with a rapid recovery. Pyometra is still a serious disease, though. In a study of Swedish insured cats from 1999 to 2006, the case fatality rate was 5.7%, and in an older US hospital series (183 cats, 1979 to 1984), 8% died or were euthanized. Those good survival odds depend on getting the infection under control, which is why speed matters.
What happens without surgery?
Some owners want to avoid surgery, usually because the cat is a breeding queen. In carefully selected cases, a medical approach is possible. It combines hormonal drugs (prostaglandins, or progesterone blockers where they are available) with antibiotics, under close veterinary monitoring. Some of these drugs are not available in the United States. This option is only for cats that are stable and not systemically ill, and the pyometra can come back after medical treatment, so spaying is usually recommended once her breeding career ends. Your veterinarian decides whether a cat is a candidate and chooses the drugs and doses.
Antibiotics alone are not a treatment for pyometra. Without effective treatment, the likely results are:
- Deterioration of health
- Increased pain
- Sepsis
- Rupture of the uterus leading to peritonitis
- Death
Prevention is simpler than any of this. The ACVS notes that most cats spayed early in life will not develop pyometra. For the veterinary team, two caveats are worth knowing. Pyometra of the uterine stump can occur after an incomplete spay that leaves ovarian tissue behind, and progestin drugs used to suppress heat can themselves cause CEH and pyometra.
Pyometra is still unfamiliar to many cat owners, so it deserves sensitivity and care when the team explains the diagnosis and recommends treatment. A clear explanation of why a routine spay prevents this emergency belongs in every conversation with the owner of an intact cat.
Originally written by Amber LaRock. Updated by the I Love Veterinary editorial team.
Sources
- Journal of Feline Medicine and Surgery: Pyometra in the queen: To spay or not to spay? (Hollinshead and Krekeler, 2016)
- American College of Veterinary Surgeons: Pyometra
- Merck Veterinary Manual: Cystic Endometrial Hyperplasia-Pyometra Complex in Small Animals
- Theriogenology: Incidence of pyometra in Swedish insured cats (Hagman et al., 2014)
- JAVMA: Pyometra in cats, 183 cases (1979-1984) (Kenney et al., 1987)
This article is for general information and is not a substitute for advice from your veterinarian.
