What is pyometra in dogs?

Pyometra in dogs is defined as a uterine infection. It is always seen in unaltered female dogs regardless of their breeding status.

Pyometra is an important disease to be aware of for any dog or cat owner because of the sudden nature of the disease and the deadly consequences if left untreated. It has been compared to acute appendicitis in humans because both are essentially empyemas within an abdominal organ.

What are the symptoms of pyometra in dogs?

The most obvious symptom of open pyometra in dogs is a discharge of pus from the vulva in a female that has recently been in heat. However, symptoms of closed pyometra are less obvious. Symptoms of both types include vomiting, loss of appetite, depression, and increased drinking and urinating. Fever is seen in less than a third of female dogs with pyometra.
Closed pyometra is a more serious condition than open pyometra not only because there is no outlet for the infection, but also because a diagnosis of closed pyometra can easily be missed due to its insidious nature. Bloodwork may show dehydration and/or increased white blood cell count. X-rays will show an enlarged uterus, and ultrasound will confirm the presence of a fluid-filled uterus.

What causes a pyometra in dogs?

Pyometra is a result of hormonal and structural changes in the uterus lining. This can happen at any age, whether she has bred or not, and whether it is her 1st or 10th heat (although it becomes more common as the dog gets older). The main risk period for a female is for eight weeks after her peak standing heat (or estrous cycle) has ended. Normally during this period, the cervix, which was open during her heat, begins to close, and the inner lining begins to adapt back to normal. However, cystic hyperplasia of the endometrium (inner lining of the uterus) – known as cystic endometrial hyperplasia (CEH) – may occur at this time for some animals, as an inappropriate response to progesterone.

Under these circumstances, bacteria that have migrated from the vagina into the uterus find the environment favorable to growth, especially since progesterone also causes mucus secretion, closes the cervix (preventing uterine drainage), and decreases uterine contractility.

Treatment of pyometra in dogs

The most important aspect of treatment of pyometra is quick action to provide supportive care. Female dogs are often septic and in shock. Intravenous fluids and antibiotics should be given immediately. Once the female dog has been stabilized, then the treatment of choice is an emergency spay.

If you would like to know more about other conditions of the female reproductive system, read about Tumors of the Reproductive System in Female Dogs.

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