Diagnosing and Treating Pyometra

What is pyometra?

Pyometra is a severe bacterial infection in the reproductive tract that causes the formation of purulent (pus or containing pus) material to develop in the uterus. This occurs secondary to hormonal changes in female dogs and cats. Following a heat cycle, hormones change, making it easier for bacteria to enter the uterus, grow, and cause an infection.  

What causes pyometra?

It is caused by hormonal changes in the body that cause the uterus to fill with pus. Intact females that still have reproductive organs are more likely to get pyometra, especially when they are over age 6. A very common organism called E. coli, found in feces, usually causes the condition. There are hormonal changes which take place in the uterus during each heat cycle and these make the infection more likely as pets get older.

Following estrus (heat), the hormone progesterone remains elevated for up to two months and causes the lining of the uterus to thicken in preparation for pregnancy. If pregnancy does not occur for several consecutive estrus cycles, the uterine lining continues to increase in thickness until cysts form within the uterine tissues (a condition called cystic endometrial hyperplasia). The thickened, cystic lining secretes fluids that create an ideal environment for bacterial growth. In addition, the muscles of the uterus cannot contract properly either due to thickening of the uterine wall or the high levels of the hormone progesterone. This means that bacteria that enters the uterus and fluids that have accumulated cannot be expelled.

During estrus, white blood cells, which would normally protect against infection by eliminating bacteria, are inhibited from entering the uterus. This normal occurrence allows sperm to safely enter the female's reproductive tract without being damaged or destroyed by these immune system cells.

Stump pyometra can occur in dogs and cats that have been spayed, if the doctor performing the surgery did not remove the entire uterus.

Progesterone-based drugs can also cause pyometra due to the changes they make in the uterus. In addition, estrogen or synthetic estrogen drugs will increase the effects of progesterone on the uterus. Drugs containing both estrogen and progesterone are sometimes used to treat certain conditions of the reproductive system. Any intact female receiving hormones must be carefully monitored for the development of pyometra.

What are the symptoms of pyometra and how is it diagnosed?

Pyometra can be "open" or "closed". In an open pyometra, the cervix is open, allowing the purulent discharge in the uterus to drain out through the vaginal opening. The discharge will usually be thick or bloody with a foul odor. The dog or cat may groom the hindquarter area excessively. In a closed pyometra, the cervix remains closed, trapping the pus inside the uterus. This type of pyometra is harder to diagnose; radiographs or ultrasound may be required for diagnosis. Closed pyometra is also more dangerous, as these animals become toxic more quickly and are subject to uterine rupture.

Pets affected with pyometra will usually drink more than usual, may have decreased appetite, and may be lethargic. They may vomit, have a bloated abdomen, and may collapse.

Symptoms generally appear six to eight weeks after going through a heat cycle for dogs, which cycle about every seven months. Pyometra most commonly occurs in cats that have been in heat within the past month.  

A complete blood count (CBC) will usually show an elevated white blood cell count, with elevated numbers of neutrophils and band cells, which signal a bacterial infection. Blood glucose (sugar) and globulins may also be elevated.

How can pyometra be treated?

In the past, the preferred treatment has been surgery. The veterinary surgeon usually performs an ovariohysterectomy (spay) to remove the infected uterus and ovaries. This surgery is more complicated than routine spay, however studies have shown high survivability over 97%, even in non-specialty clinic settings.

Pets diagnosed in the early stages of their illness are considered good candidates for a successful surgery. The risks of complications and extended hospitalization are higher if diagnosis is delayed.

After the surgery, typically, intravenous fluids (IV) are needed; the pet may remain hospitalized for two to three days on fluids and antibiotics.

Pyometra is a medical emergency that needs immediate treatment. If you notice symptoms or changes in your pet's behavior, call your veterinarian. Early diagnosis lowers the risks of complications. If left, the disease will worsen to the point of dehydration, collapse, and death from septic shock. Closed pyometras that go untreated can result in uterine rupture, peritonitis, and a worse prognosis for recovery.

There is a medical approach to treating pyometra, although the success rate is highly variable and not without considerable risk and potential long-term complications.

Prostaglandins are a group of hormones that lower the level of progesterone in the blood, relax and open the cervix, and cause the uterus to contract, therefore expelling the bacteria and pus. They can be used to treat this disease, but they are not always successful and have some important limitations.

  • 1.   Prostaglandins cause side effects including restlessness, panting, vomiting, defecation, salivation, and abdominal pain. The side effects occur within minutes after administration and can last for a few hours. They become progressively milder with each successive treatment. 
  •  2.   It takes approximately forty-eight hours for the prostaglandins to take effect, so pets that are severely ill and need immediate life-saving treatment are poor candidates.
  •  3.   Because prostaglandins cause the uterus to contract, it is possible for the uterus to rupture and spill infection into the abdominal cavity resulting in the severely life-threatening condition known as peritonitis. This is most likely to happen when the cervix is closed.

The use of prostaglandins to treat pyometra has variable rates of success. Prostaglandins do not prevent recurrence of the disease; successful breeding in the future is not guaranteed.

Aglepristone is a progesterone antagonist that has been used to treat pyometra in both dogs and cats. It is labeled for use to induce abortion after unwanted mating. In bitches with closed cervix pyometra, administration of aglepristone is often followed by cervical opening within 24-48 hrs. There is no information on the effect of aglepristone on pyometra in the queen, but efficacy for this indication is thought to be the same as in dogs.

Homeopathic protocols exist for treatment of pyometra; work with a trained veterinary homeopath to be sure treatment is helping. TCVM (Traditional Chinese Veterinary Medicine) approaches to therapy may include acupuncture and herbal therapy. These modalities may be combined with traditional therapies. 

Can my pet be bred again after being treated for pyometra?

Many dogs and cats can be bred after successful treatment for pyometra. The pet owner should be vigilant for any symptoms of pyometra after future heat cycles.

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