Pyometra is a life-threatening bacterial infection of the uterus that occurs in intact (unspayed) female dogs and cats. The uterus fills with pus, and without emergency surgical treatment, the condition is fatal. It typically occurs in middle-aged to older females 4–8 weeks after a heat cycle. Spaying completely and permanently prevents pyometra.
Pyometra develops because progesterone levels after oestrus thicken the uterine lining and suppress local immune responses, creating an ideal environment for bacterial colonisation — usually by E. coli bacteria from the gastrointestinal tract. The condition exists in two forms: open cervix pyometra, where pus drains vaginally (visible as a foul-smelling discharge), and closed cervix pyometra, where the cervix is closed and pus builds internally — the more dangerous form because it shows fewer external signs.
Symptoms vary by type. Open pyometra: foul-smelling vaginal discharge, increased water intake and urination, lethargy. Closed pyometra: more subtle and rapidly life-threatening — distended abdomen, vomiting, severe lethargy, and collapse without obvious discharge. Any intact female dog or cat showing lethargy, increased drinking, or abdominal distension 4–8 weeks after a heat cycle should be seen urgently.
Emergency surgical spaying (ovariohysterectomy) is the treatment of choice and is curative. Medical management with prostaglandins exists but is reserved for breeding animals, carries a lower success rate, and carries significant risk — it is not appropriate for severe or closed cases. Recovery after successful surgery in otherwise healthy animals is typically excellent.
📌 Key Facts
Only affects: Intact (unspayed) females
Timing: Typically 4–8 weeks after heat cycle
Most dangerous form: Closed cervix (internal pus accumulation, minimal external signs)
Treatment: Emergency spaying | 100% preventable by spaying
Frequently Asked Questions about Pyometra
Q: How quickly does pyometra become life-threatening?
Closed pyometra especially can deteriorate rapidly — a dog or cat that was walking around 24 hours ago can be in septic shock within a day or two of uterine rupture or toxin absorption. If you suspect pyometra, do not wait overnight to see if symptoms improve. This is an emergency.
Q: Can pyometra recur after medical treatment?
Yes. Medical treatment suppresses the current infection but does not change the underlying susceptibility. Many intact females treated medically for pyometra develop it again within 1–2 years. Surgical spaying after recovery is strongly recommended unless the animal is actively needed for breeding.
Q: At what age does pyometra most commonly occur?
It most commonly affects middle-aged to older intact females (typically 6+ years in dogs, though it can occur at any age after sexual maturity). The cumulative effect of repeated progesterone exposure with each heat cycle progressively increases risk over a female's lifetime.
⚠ Medical Disclaimer: This glossary entry is for educational purposes only
and does not constitute veterinary advice. Always consult a licensed veterinarian for diagnosis
and treatment of your pet's health conditions.