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Pyometra/Pyometritis – An Emergency!!!

Updated: Sep 19, 2021



Pyometra is a disease condition common in un-neutered female dogs that demands a major surgery as treatment. Though profoundly serious, the response to treatment is good with full recovery expected. Neutering is the best way to protect a female pet against pyometra.

What is Pyometra/Pyometritis?


Pyo = pus, infection; metra = womb or uterus

Pyometra is a life-threatening infection of the womb (uterus) causing the accumulation of pus within the space of this organ. The uterus is where the growing foetus is located during pregnancy. Pyometra is common in older, female cats and dogs who have not been neutered, and must be treated quickly and aggressively.

How is Pyometra/Pyometritis classified?


Pyometra may be classified as either open pyometra or closed pyometra. Open pyometra is characterized by a discharge from the vagina that may be bloody or yellow or cream-coloured. A closed pyometra, on the other hand, has no discharge to the exterior. When pus does not drain out through the vagina, the patient becomes very ill and develop blood poisoning (toxaemia). The existence of this poison in the body leads to life-threatening situations such as kidney failure. Untreated, pyometra leads to death from dehydration, toxaemia and kidney failure.

Pyometra in a bitch being spayed

Another form of pyometra that is less common is stump pyometra. Stump pyometra occurs in females who have been spayed (neutered), but a small piece of the womb remains that become infected. Since only a small amount of the womb remains, clinical signs tend to be less severe. However, to prevent complications, this condition also needs to be treated.

What causes Pyometra/Pyometritis?


Pyometra is usually due to hormonal changes in the reproductive tract subsequently after oestrus ("heat") in the dog. The levels of the female pregnancy hormone progesterone remain elevated for eight to ten weeks thickening the lining of the uterus in preparation for pregnancy. If pregnancy does not occur for several oestrus cycles, the uterus lining continues to increase in thickness until cysts form within it. The thickened, cystic lining secretes fluids that create an ideal environment in which bacteria can grow. Additionally, high progesterone levels inhibit the ability of the muscles in the wall of the uterus to contract.

Escherichia coli bacteria

Annually, a bitch comes on heat twice and undergoes all the hormonal changes associated with pregnancy - whether she is pregnant or not. With each cycle, the changes in the womb make the infection more likely with age. Infection is usually caused by a very common bacteria called E. coli, and frequently occurs in the weeks or months following a heat or season period. Hormones injected to stop seasons or for treatment of other conditions are able to also increase the risk of pyometra developing. Besides, oestrogen increases the effects of progesterone on the uterus, and drugs containing both hormones are often used to treat certain conditions of the reproductive system.

How does pus develop in the uterus?


The cervix is the door to the uterus and remains firmly closed except during estrus. When open, bacteria that are normally found in the vagina enter the uterus quite easily. In a normal uterus, the environment is unfavourable to bacterial survival; however, when the wall of the uterus is thickened and cystic, it is a perfect condition for bacterial growth. Besides, with these abnormal conditions, the muscles of the uterus cannot contract properly, meaning that bacteria that enter the uterus cannot be expelled.

What are the signs of Pyometra/Pyometritis?


Pyometra is definitely a females’ condition (since males do not have a womb). It commonly occurs in older females (above 6 years of age), and the signs usually develop just about 6 weeks after her last season. Initially, the signs of pyometra are not very obvious. However, the following might be noticed:-

1. The bitch might just be licking her back end more often than usual.

2. She might be off colour and off her food.

3. Panting and weakness

4. Frequently she might be very thirsty, hence drinking so much water starting to wet in the house.

5. Occasionally, pus escapes from the womb (a reddish-brown or yellow discharge may be seen at the vulva).

6. As the condition progresses, she gets more ill and may start to vomit, become very depressed and unwilling to get out of her bed.

7. Bloated abdomen

8. If untreated, signs progress to dehydration, collapse and death from toxic shock.

How is Pyometra/Pyometritis diagnosed?


Diagnosis of Pyometra/Pyometritis is by:-

1. History - description of the symptoms.

2. Tests to confirm the diagnosis and also to make sure that your pet is well enough to withstand an operation.

Laboratory for testing blood, etc

a. Blood tests to see if the toxins from the infection have entered the blood and could be affecting organs elsewhere.

b. X-ray and ultrasound examinations to confirm that the uterus is enlarged.

How is Pyometra/Pyometritis treated?


Pyometra is an emergency!!!

Once diagnosed, the bitch should be operated immediately to remove her womb. It is the same operation carried out routinely to spay or neuter a female cat or dog. However, in an animal ailing from pyometra, it has more risk. The risk is even higher if not operated, with most animals dying if surgery is not performed. If the uterus is not removed, toxins are released from the infection which gets into her blood and makes her more ill. Eventually, these toxins can cause kidney failure.

Drip for a dog with pyometra

Before performing the operation, the animal is given some fluids (into her vein) and antibiotic treatment. Surgery might be delayed for 12-24 hours to give the animal time to be in a better condition to tolerate the surgery. The animal may need hospitalization after surgery for continued treatment.

In certain situations where the bitch is valuable for breeding, dogs have been treated with special hormone injections to empty the womb without having to perform an operation. However, this treatment is often not successful.

In very old animals with pyometra and clear evidence of organ failure (eg kidney and liver failure), or where other major problems such as serious heart disease exist, euthanasia may be the kindest option.

Do dogs recover from Pyometra/Pyometritis?


Pyometra is a serious disease and unfortunately, a proportion of patients do not pull through despite treatment, owing to organ failure and complications. Overall, many dogs and cats do recover remarkably well and it is certainly well worth pursuing treatment.

How is Pyometra/Pyometritis Prevented?


Neutering is the only way to ensure that an animal wont develop this condition. If the bitch is not intended for breeding, then neutering at a young age as possible is the best prevention. If a female is neutered before her first season, she is also protected against breast cancer developing in later life.

Pyometra may be more common in bitches that are not neutered and have never had puppies, however, it is not exclusively a disease of these animals. Breeding does not guarantee protection and indiscriminate breeding of pet dogs and cats is not to be encouraged.



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Bedrica L, Sacar D (2004): A case of atypical hyperplasiapyometra-complex in a female dog (in German). Tierarztliche Umschau 59, 433–439.

Bigliardi E, Pamigiani E (2004): Ultrasonography and cystic hyperplasia-pyometra complex in the bitch. Reproduction in Domestic Animals 39, 136–240.

Blendinger K, Bostedt H (1991): The age and stage of estrus in bitches with pyometra. Statistical inquiry and interpretive study of the understanding of variability (in German). Tierarztliche Praxis 19, 307–310.

Blendinger K, Bostedt H, Hoffmann B (1997): Hormonal state and effects on the use of an antiprogestin in bitches with pyometra. Journal of Reproduction and Fertility 51, 317–325.

Borresen B (1979): Pyometra in the dog. I. A pathophysiological investigation. II. Anamnestic, clinical and reproductive aspects. Nordisk Veterinaermedicin 31, 251–257.

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