Pyometra is the most common disease of the uterus affecting intact female dogs and cats. The incidence in dogs has been reported to range from 9-15.2%, with older nulliparous bitches (those that have never given birth) at greatest risk.

Dogs with pyometra develop an infection of the uterus due to colonization of the tissue with bacteria. The most common bacteria identified in these cases is E. coli.  This is a potentially life-threatening condition due to the secondary complications of infection that can ensue including sepsis, shock, and Systemic Inflammatory Response Syndrome (SIRS).

Pyometra most commonly develops during diestrus or after an animal has been administered exogenous progestins. The clinical signs are variable and can include lethargy, loss of appetite, vomiting, as well as increased thirst and urination. Affected pets may also have a fever and/or vaginal discharge, however these do not develop in all cases.

Diagnosis is made based on a review of the pet's history and physical examination findings. Other tests that may be performed or required to make the diagnosis include abdominal radiography (x-ray) or ultrasound, bloodwork including a complete blood count (CBC), and cytologic examination of vaginal or vulvar discharge (if present).

The recommended treatment is often ovariohysterectomy (spaying the female). However, valuable breeding animals can often be successfully treated non-surgically with a combination of supportive care and medical therapy including prostaglandins, dopamine agonists, progesterone antagonists, and antibiotics. These treatment protocols can become costly, time-consuming, and are not without risk themselves. In addition, up to 25% of cases that seem to respond to medical therapy can subsequently recur or relapse.

At the 2017 AKC Canine Health Foundation National Parent Club Canine Health Conference, Dr. Marco Coutinho da Silva explained more about pyometra and one mechanism to explain why this disease can be difficult to treat or can be recurrent or persistent in some bitches. Our understanding of this mechanism is foundational for developing new forms of therapy and management of affected dogs:

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