By Dr Chantal Moreton BVSc

Pyometra is a dangerous condition that few people are aware of until faced with a very unwell dog who usually needs emergency surgery.

It is a condition seen in older dogs more commonly, who have had regular 6 monthly heats but never been pregnant.  It results from repeated exposure of the uterine lining to high concentrations of the hormones oestrogen and progesterone which causes cystic endometrial hyperplasia (i.e. unhealthy uterine lining).  When a dog is in heat, the cervix becomes partially opened and bacteria enters the uterus from the vagina and the unhealthy uterine lining creates the perfect environment for the bacteria to multiply.  Eventually the uterus becomes enlarged with a purulent (pus) filled discharge.  The infection can enter the blood stream (septicaemia) and spread to other organs, especially the kidneys and liver.

This process happens slowly over time and dogs often show no clinical signs of disease until they are very unwell – not eating or drinking, dehydrated, vomiting.  Sometimes there is evidence of disease with a vaginal discharge (an open pyometra) but with no discharge, the pus has nowhere to escape (a closed pyometra) and this can lead to rupture of the uterus and peritonitis – a catastrophic event!


Diagnosis is suspected when a female, unspeyed dog presents with signs of being unwell, an enlarged abdomen and has usually been in heat within the past 12 weeks.  An x-ray or ultrasound will show signs of uterine enlargement and blood tests may show evidence of infection, kidney and/or liver disease. 

If the condition is mild and owners still want to breed with the dog, sometimes antibiotics and hormone therapy will clear the infection and future pregnancy may improve the health of the uterus.  It would still be recommended to spey her as soon as possible though.

However, usually these dogs are very unwell and they need life-saving treatment.  This usually means starting on high doses of antibiotics, i/v fluid therapy to help with hydration and kidney/liver function.  Once (and if) stable, an emergency spey (hysterectomy – removal of both ovaries and the uterus) is required.  As you can imagine, this is a high risk surgery with potential for rupture of the uterus – an unhappy situation for both the dog, owner and veterinary team!

The good news is that once the surgery is performed and if normal organ function is restored, patients go on to live a normal, healthy life but it is a very risky time for them and not all dogs will survive.

So… always the best cure is prevention!!!  Spey your female dogs at an early age (preferably before their first heat at about 5-6 months of age) and this nasty condition can be avoided.  However if you do suspect your dog may have a pyometra, please bring her in early to be assessed, remind your vet that she is unspeyed and we can give her the best chance of getting through this nasty disease.

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