Pyometra is a life-threatening infection of the uterus seen in middle-aged to older non-desexed female dogs 8 to 12 weeks after coming into season. It’s much less common in cats, and occurs around 4 weeks after a season.

Hormonal imbalance causes changes to the uterus lining and the secondary infection that follows is serious – pyometra literally means ‘pus-filled uterus’.

Pyometra can be open or closed. When the cervix remains open, pus can escape from the uterus. This makes diagnosis easier as the discharge is obvious, and the dog is not as critically ill.

When the cervix stays closed, the pus builds up in the uterus and can’t escape – it’s not uncommon for our vets to remove a pus-filled uterus that weighs over a kilo.

Above left: a simple diagram showing the two horns of the canine (and feline) uterus - one normal, on the right, affected by pyometra.
Centre and right: CVH vet operating on a medium-sized kelpi to remove a closed pyometra weighing 2kg. The middle-aged dog became acutely ill after being off-colour for a few days and was extremely ill when presented to CVH. Stabilised with I/V fluid therapy and antibiotics, she survived the major surgery. The owner is now making sure all his non-breeding working dogs are desexed.

Symptoms

The resultant severe infection causes bacterial endotoxins to enter the blood stream, affecting the function of all body organs. The pet becomes extremely ill and diagnosis is based on clinical history (ie the pet is non-desexed and has had a recent season), blood counts, ultrasound, and symptoms that include fever, excessive drinking and urinating, abdominal enlargement, vomiting, depression and weakness.

Treatment

Once diagnosed, the sick pet is stablised with intravenous fluids and antibiotics before surgery to remove the infected uterus. The ovaries are also removed as in routine desexing. Intensive care is required to counteract the effects of the severe infection and to support recovery.

Prevention

Desexing female pets prevents pyometra. Even if a dog is middle-aged or older, please speak with us about desexing – it’s safer to desex a middle-aged pet than to risk potentially fatal infections of the uterus.