Pyometra in Dogs & Cats
Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS
Table of Contents
Pyometra is an infection within the uterus (womb). It affects approximately 25% of un-neutered female dogs and can affect un-neutered female cats. In some dogs, ongoing hormonal cycles cause the uterine lining to become thickened and develop cysts, known as cystic endometrial hyperplasia. This can develop into a pyometra over time.
The average age for development of pyometra is eight years old in dogs, and five years old in cats, however it can occur much younger in some dogs. If pyometra is untreated it can be fatal, so rapid management is essential.
Pyometra typically occurs within eight weeks of a dog's season (when a female dog is fertile). Cats do not cycle the same way, so are less predictable.
- increased thirst and urination
- lack of appetite
- abdominal pain
If the cervix is open (known as “open pyometra”), there may be yellow, pink or brown coloured discharge from the vulva or an increase in grooming behaviour.
If the cervix is closed (known as “closed pyometra”), the infection is trapped, and the abdomen may become swollen. If treatment is delayed, the toxins from the pyometra can spread around the body and the uterus can rupture. This causes fever, rapid heart rate, collapse and can ultimately be fatal.
Examination, symptoms and timing are likely to raise a high suspicion of pyometra, however they are not a diagnosis alone. Imaging is required to assess the uterus and confirm infection. Ultrasound is commonly used, and can often be done with the patient awake, but pyometra can also be visible on x-ray.
Blood tests are routinely advised. These may show changes often seen with pyometra, such as high white blood cell count (markers of infection) and dehydration. Blood tests also allow organ health to be screened and may influence what drugs we use; older animals are more likely to have other problems and, sometimes, toxins from the pyometra can affect the liver or kidneys.
Surgery is the treatment of choice for most dogs with pyometra. Surgery involves removal of the uterus and ovaries so prevents recurrence of pyometra in future. If patients are very unwell at the point of diagnosis, stabilisation with fluids (a drip) may be required before they are fit for anaesthesia. Depending on the age and health of the pet, they may be able to go home the same day or may be advised an overnight stay in hospital.
If surgery is not possible, medical treatment can be attempted. This involves antibiotics and a series of injections to open the cervix and encourage the uterus to expel the infection. Medical treatment is not always successful and is not suitable for pets who are generally unwell. It should be used cautiously in cases with a closed pyometra. If medical treatment is effective, a routine spay will need to be performed at a later date, otherwise the pyometra is likely to reoccur after future seasons.
The prognosis after pyometra surgery is excellent, and most patients will make a complete recovery with no lasting effects.
Patients who are very unwell, or who suffer a uterine rupture, have a more cautious prognosis as these are much more challenging to treat. These patients are likely to need a longer stay in hospital and more intensive treatment.
Patients treated medically can do well; however, if treatment is not successful, there is a risk these patients can deteriorate rapidly and need urgent surgery.
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Please note that the content made available on this webpage is for general information purposes only. Whilst we try to ensure that at the time of writing all material is up to date and reflects industry standards, we make no representation, warranties or guarantees that the information made available is up to date, accurate or complete. Any reliance placed by yourselves is done so at your own risk.
Page last reviewed: 7th August 2023
Next review due: 7th August 2025