Last Updated: 15/12/2025
Pyometra in Dogs: Signs, Treatment, and Prevention of a Uterine Infection
Pyometra is a serious, life-threatening infection of the uterus that affects un-desexed female dogs. Learn the key signs (like unusual discharge or lethargy), the difference between open and closed pyometra, and the importance of emergency treatment.
Author: Dr Emilee Lay BVSc BSc (Vet) Hons
Reading Time: 6 minutes - short read
Have you recently heard the term pyometra and are worried about your entire (un-desexed) female dog? Pyometra is a serious, life-threatening uterine infection that occurs in all sexually intact female dogs, and it is considered a genuine veterinary emergency. The good news is that we know exactly how to prevent it and how to treat it. Read on to learn exactly what pyometra is, the critical signs to look out for, the treatment options available, and the best way to ensure your dog never has to face this condition.
What is pyometra in dogs?
Pyometra is an infection of the uterus, brought about by hormonal changes that occur following a heat or "oestrus" in dogs. Following a heat or period, progesterone (a hormone produced by the body) stays elevated - preparing the uterus for pregnancy by helping to thicken the lining. With subsequent heat cycles (that aren't followed by pregnancy), the lining continues to thicken and form cysts which secrete fluids that create an ideal environment for bacteria to flourish.
The causes and risk factors for pyometra
Bacteria that cause Pyometra, are normally found in the vagina and tend to take advantage of an ideal environment to grow. This ideal environment is created when the thickened and cystic uterine wall facilitate bacterial growth. A normal, healthy uterus is generally a hostile environment for bacteria. Bacteria enter the cervix - which is normally closed- during oestrus, where it stays open.
High levels of progesterone can also reduce the ability of the muscles of the uterus to contract, thus the uterus cannot expel the bacteria. The most common window of time for a Pyometra to occur is between 2-8 weeks after a heat.
Risk Factors for Pyometra
- Being a female, entire dog is the main risk factor for Pyometra.
- This condition can occur at any age, but is more commonly seen in mature dogs.
- Dog's who have recently been mated or inseminated are also at risk.
- Dog's on progesterone and oestrogen based drugs are also at an increased risk of Pyometra.
Signs and symptoms of pyometra (open vs closed)
Pyometra comes in two "types"- open and closed. The clinical signs your dog shows will depend on which type of infection she has.
Open pyometra
In an open pyometra, the cervix (the gateway to the uterus) stays open, allowing pus to drain from the uterus.
- Key sign: Abnormal, often foul-smelling, discharge from the vulva following the end of a heat cycle.
- Dogs with open pyometra may not immediately show severe general signs like fever, lethargy, or loss of appetite, making it harder to spot early.
Closed pyometra
In a closed pyometra, the cervix is closed, trapping the pus inside the uterus. This is often more immediately dangerous.
- The pus builds up, which can cause the abdomen to appear bloated or distended and feel uncomfortable or painful.
- Bacteria and their toxins enter the circulation quickly, resulting in severe illness.
Symptoms seen in both types
Whether the cervix is open or closed, the bacterial toxins affect the kidneys, leading to:
- Increased thirst
- Increased urination
General signs of systemic illness (especially with Closed Pyometra):
- Lethargy (extreme tiredness)
- Inappetance (loss of appetite)
- Vomiting
- Diarrhoea
- Depression
How veterinarians diagnose pyometra
Physical examination is always the first step in diagnosing any disease. Female, entire dog's who are displaying any of the clinical signs are always suspected of having a pyometra, especially if they have come off of a heat or have a painful, enlarged abdomen.
Bloodwork of affected dog's may show an elevated white cell count with elevated protein markers associated with the immune system. The urine may also be quite diluted. However imaging in the form of an X-ray or ultrasound is far more diagnostic, as it can show an enlarged fluid filled uterus.
Treatment options for pyometra
Surgery
As Pyometra can be a life threatening condition - the most effective treatment that minimises risks is surgery to remove the ovaries and the uterus - much like in a spay or ovariohysterectomy. However, this surgery is complicated by the fact that many dogs are unwell, or have an overly large pus filled uterus, so extra care, hospitalisation and surgery time are needed in order to safely remove it and keep your dog stable. A course of antibiotics is sometimes needed post operatively. Desexing your female dogs is the best way to prevent a pyometra from occurring.
What happens if I want to breed from my dog in the future?
Surgery is the main treatment for Pyometra. Although there are medical approaches their success rate is variable, and carry an increased risk of long-term complications. Prostaglandins are hormones that can be used to lower progesterone thus opening the cervix, relaxing and contracting the uterus to expel out the pus. These hormones can have significant side effects and are not suitable for dogs who are severely unwell. There is also a risk of the uterus rupturing as it contracts - especially if it is a closed pyometra.
Speak to your vet about the success rates, likelihood of reoccurrence and the ability to breed in the future if electing for medical management.
How to prevent pyometra in dogs
Desexing your female dog completely eliminates and prevents pyometra. Desexing can be done from six months of age, or if your dog has recently had a heat then about 2 months after the end of her season.
Check out our article on Desexing - Everything You Need to Know to find out more.
What about dogs that have been recommended to delay their desexing?
There have been some recent studies suggesting potential benefits for delayed desexing in certain breeds (namely large and giant breeds) of dogs. This is a discussion to have with your vet, weighing up the pros and cons of delayed desexing. Dr Abbie Tipler has a great article on this topic - which can be found here.
FAQs
Pyometra is a very serious, and sadly common, condition in entire female dogs. Recognising the subtle signs, especially in the 2 to 8 weeks following a heat cycle, is crucial for saving your dog's life. While surgery is the main form of treatment for an emergency pyometra, the absolute best news for pet parents is that it is 100% preventable. If you have an un-desexed female dog, speak to your veterinarian about the best time to book in for a desexing procedure.
Articles recommended for you
What to expect when your dog is expecting! Our vets guide to pregnancy in dogs.
Learn how to manage heat in your dogs.
Thinking about desexing your pet? Find out all you need to know about to prepare your pet.
See our guide to protecting your pet from parasites from our vet team.
Intestinal worms are sneaky invaders that can affect your dog's health and even your family. From roundworms to tapeworms, discover the best ways to spot the symptoms and choose the right vet-approved prevention to keep your household worm-free.
Does your pet suffer from anxiety? Check out our Vet-guide for treatment options to help your pet.
History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Tue 16 Dec 2025
Edited by Dr Gillian Hill BVSc (Hons)Dr Emilee Lay BVSc BSc (Vet) Hons
Veterinarian
Dr. Emilee graduated from the University of Sydney in 2018 with a Bachelor of Veterinary Science and Bachelor of Science (Veterinary Studies) and as a student worked for a number of years as a small animals and exotics nurse in clinics across Sydney. She is currently a practicing small animal and exotic vet along the Coast. Emilee holds a special passion for avian and exotic medicine (bunnies being her favourite patients), as well as animal behavioural medicine!
