Pyometra In Dogs And Cats

Pyometrais a condition of the “intact” or un-spayed female dog or cat.

Mindy Sue, after lifesaving pyometra-removal surgery.

The Greek prefix “pyo” means “pus,” and the suffix “metra” refers to the uterus. Therefore, the literal translation is “pus in the uterus,” but the condition is more complex than that. Some clinicians use the term pyometritis. The “itis” suffix refers to the inflammatory component of the condition.

Pyometra has its beginnings rooted in the heat cycle, which causes swelling of the uterus, thickening of the uterine walls and collection of fluid in the lumen, or cavity of the organ. After repeated heat cycles, more fluid collects, creating a rich culture medium in which bacteria can grow.

Pet owners may notice their dog or cat drinking more and eating less. There is sometimes a vaginal discharge, which may be foul-smelling, bloody, or absent. Infection is often preceded by irregular heat cycles and pseudopregnancy, or false pregnancy. During pseudopregnancy hormone levels soar out of balance and fluid accumulates in massive amounts.

In pyometra the uterus is filled with pus and can become 30 times larger than normal.

If a practitioner suspects pyometra from his physical examination, he may next perform laboratory tests. A Complete Blood Count (CBC) usually shows an elevated white blood cell (WBC) count. WBCs can be elevated to two or more times normal. White blood cell counts of 100,000 are sometimes seen in longstanding cases. Such patients are typically very ill.

A low red blood cell (RBC) count may also be present, indicating anemia caused by chronic inflammation and/or blood loss in the vaginal discharge.

Infections in the uterus often leak toxic byproducts into the bloodstream, poisoning the body from within. Therefore, the chemistry profilewill often reveal damage to the liver and/or kidneys. Such damage is usually reversible with successful surgical removal of the infected uterus.

The uterine horn on the left has been incised, exposing extreme pus at the top (near the ovary) and extreme uterine wall thickening throughout.

Other helpful diagnostic procedures include abdominal X-ray and abdominal ultrasound. Uterine size can vary from pencil-sized to several inches in diameter. Smaller uteri are seen when the cervix is open and infection drains at least partially. Uterine size comparable to a balloon ready to burst occurs when the cervix acts as a seal as infection festers.

A uterus of normal diameter is virtually impossible to see on a radiograph, whereas ultrasound is much more sensitive and may even give some information about the contents of the inside of the uterus.

In valuable breeding stock, non-surgical treatments for pyometramay be considered, in hopes of successfully

In the foreground see pools of pus, at the top notice hemorrhage, which accounts for the bloody vaginal discharge the owners observed.

draining the infection and returning the pet to fertility. Prior to entering into this process, however, the pet owner must be aware that the life of the pet hangs in the balance. Not only are success rates low, but some of the medications used are harsh and rupture of the infected uterus often results in death.

Surgical removal of the uterus and ovaries is the standard of care and is successful in the vast majority of cases. Obstacles can include the aged patient, those toxic from the disease, complicating factors such as diabetes and rupture of the uterus. Fortunately, when a pyometra case spills its infection during surgery the prognosis is better than rupture during medical treatment, because the abdominal cavity is already open and can be aggressively irrigated and disinfected.

Thanks to modern anesthetics and careful monitoring, even pets with diabetes, kidney disease and less-than-perfect livers may have safe surgical removal of an infected uterus.

As is usually the case, prevention is much easier. Have your female dog or cat spayed at a young age and pyometra is a nightmare that will never wake you up from your sound sleep.

See you tomorrow, Dr. Randolph.


  1. My dog had Pyometra surgery. She was diagnosed with anemia, the medication she was given isn’t working well. Now her Dr wants me to take her in to a specialist because the medication that can be offered they do not have at this location. Would it just be better to get a blood transfusion at this point or maybe euthanasia since my dog is old. I’m not very familiar with anemia in dogs.

  2. My dog, a miniature schnauzer, was pregnant with her 3rd litter following a surgical implant of frozen semen. The pregnancy was confirmed (at least 3 puppies were seen on ultrasound 26 days later and a blood progesterone was 78. Around 6 almost 7 weeks she lost her round belly. 3 days before the due date she began nesting and would not eat. 24 hours later I took her to the veterinarian she had an emergency operation and had to be desexed. The diagnosis was pyometra. I am a midwife and was present for the surgery. The uterus was full of a thick brown pus and it did not smell. The veterinarian said he thought it was decomposed puppies as there were bits of membrane. Now my girl has heaps of milk and is mothering one of her toys. Please can you explain what exactly has happened? It is extremely sad to watch and I wish there was an orphan puppy who could help.

    • Dan, your situation certainly is heartbreaking. As stated in our article on pyometra that you have already read, pyometra is almost always caused by an imbalance of hormones. Was your dog artificially inseminated because she had difficulty becoming pregnant conventionally, or because you desired the specific sire’s genes? If the former, that could have been your first hint that “things” weren’t quite right internally with all of the systems required to cooperate to begin and maintain a pregnancy. In any case, clearly she became pregnant before things went awry. It is not unusual for dogs already harboring a uterine infection to become pregnant but be unable to maintain the pregnancy. Ask your veterinarian about alternating cool and warm compresses on her mammary glands until the swelling and milk production subside. He may also authorize application of topicals. We are sorry for your loss. Thank you for reading, Dr. Randolph.

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