Canine Pyometra. What Causes It, Treatment And How To Prevent It

Canine pyometra is an inflammation of the uterus that can have serious consequences for your dog. It occurs more frequently in females over the age of six who have not had cubs .

Its development is strongly influenced by progestational stimulations of the uterus during the right-handed or due to treatment with progestins , which are synthetic products similar to progesterone.

The pyometra occurs during or immediately after the luteal phase of the estrous cycle and its symptoms are very varied, depending on each case. Its early recognition, diagnosis and treatment are very important as it requires urgent veterinary attention.

Table of Contents

  • The phases of the canine reproductive cycle
  • What is canine pyometra?
    • Open pyometra.
    • Piometra closed.
  • How do bacteria enter the uterus?
  • What are the causes of canine pyometra?
  • What breeds can suffer canine pyometra?
  • What are the symptoms of canine pyometra?
    • If the cervix is ​​open.
    • If the cervix is ​​closed.
  • How canine pyometra is diagnosed
  • Canine pyometra treatment
  • My bitch is valuable for breeding. Is there an alternative to sterilization?
  • What can I do to prevent canine pyometra?
  • Conclusions

The phases of the canine reproductive cycle

The canine reproductive cycle, also called the estrous cycle , is the period between two ovulations. It consists of several phases:

  • Period of 3 or 4 months in which the reproductive system is at rest.
  • It lasts between 7 and 10 days. During this phase a bloody vaginal discharge appears. In the proestrus, males are attracted to the female, but the female does not accept mounting.
  • Zeal phase in which the female is fertile and accepts the mount. There is no longer bleeding, but the vulva increases in size. It lasts between 7 and 10 days and it is time for ovulation.
  • It coincides with the luteal phase. The female refuses to mount and there are no signs of ovarian activity.

What is canine pyometra?

Canine pyometra is a secondary infection due to hormonal changes that occur during the female’s reproductive cycle .

After heat, the levels of the hormone progesterone remain elevated for a period of time that can last up to two months. This causes the lining of the uterus to thicken , in preparation for pregnancy.

If pregnancy does not occur for several consecutive heat cycles, the uterine lining may continue to thicken until cysts form in the uterine tissues. This condition is called cystic endometrial hyperplasia.

Cystic endometrial hyperplasia develops in most sexually intact bitches as they age due to chronic and recurrent exposure of the endometrial lining to progesterone produced by the corpus luteum during the right-handed. Progesterone acts on the endometrial glands, stimulating their secretions. It also induces closure of the cervix.

The thickening of the cystic lining secretes fluids that provide an ideal environment for bacterial growth . Because the muscles of the uterus cannot contract properly, bacteria enter the uterus when it relaxes during estrus . Also, the fluids that have accumulated cannot be expelled , which causes the uterus to enlarge and inflame the abdomen of the bitch.

During heat, white blood cells, which normally protect against infection by killing bacteria, are inhibited from entering the uterus . Under normal circumstances, this situation allows sperm to safely enter the female’s reproductive tract without being destroyed by these cells of the immune system. In the case at hand , it can lead to a life-threatening infection in the dog, called a pyometra .

There are two types of canine pyometra :

Open pyometra.

At the pyometra with the cervix open , the cervix relaxes and releases a large amount of pus. Bitches with an open pyometra do not seem as sick as those with a closed cervix.

Piometra closed.

In the pyometra with the cervix closed , when it does not drain, the uterus enlarges, producing a painful inflammation in the lower abdomen. It is usually accompanied by vomiting and diarrhea and can produce signs of toxicity , such as high fever , tachycardia, and shock.

How do bacteria enter the uterus?

The gateway to the uterus is the cervix . During heat, it relaxes to allow sperm to penetrate the uterus.

If the uterus is normal, its environment prevents the survival of bacteria. However, when the uterine wall thickens or becomes cystic due to cystic endometrial hyperplasia , the ideal conditions for bacterial growth occur . At this time, bacteria, normally found in the vagina, can easily enter the uterus through the cervix.

What are the causes of canine pyometra?

The vagina is not a sterile environment . In it, many bacteria live, which are the same that have been detected in the uterus of females with pyometra. This suggests that the probable source of uterine infection is bacteria from the bitch’s own body , and not exogenous bacteria.

However, bacterial contamination of the uterus is not solely responsible for the development of the pyometra . Vaginal bacteria normally cross the cervix into the cervix when the cervix is ​​open (during proestrus and estrus), but pyometra does not develop routinely, so other uterine factors are believed to predispose to progressive infection of the uterus.

It appears that cystic endometrial hyperplasia is a prerequisite for the development of pyometra .

The use of progesterone – based drugs can cause changes in the uterus similar to the cycle of zeal. Furthermore, although estrogens do not cause cystic endometrial hyperplasia, they do increase the effects of progesterone . Estrogens administered in the form of a contraceptive injection, to prevent unwanted conception in a bitch, have been associated with an increased risk of pyometra , therefore their use for this purpose is not currently recommended.

What breeds can suffer canine pyometra?

Pyometra can occur in any young or middle-aged female, especially if it is sexually intact , although it is more common in older bitches . This inflammation usually occurs two to eight weeks after the last heat.

Although pyometra can occur in any breed, some of them are more predisposed to suffer this uterine inflammation. These breeds include the Rough-haired Collie , the Rottweiler, the Miniature Schnauzer, the Cavalier King Charles Spaniel, the Golden Retriever , the Bernese Bernese Mountain Dog, and the English Springer Spaniel.

The breeds least prone to pyometra are believed to include the Drever, the German Shepherd , the Dachshund, and the Swedish Hounds.

What are the symptoms of canine pyometra?

Canine pyometra symptoms appear one to two months after the rutting period. The most frequent are:

  • Depression.
  • Loss of appetite
  • Very thirsty.
  • The bitch urinates frequently.
  • Vomiting
  • Diarrhea.
  • High fever. Bitches with pyometra can also have a normal or even below normal temperature.

Depending on whether the cervix remains open or closed, your dog may present different symptoms:

If the cervix is ​​open.

The pus will come out of the uterus out through the vagina. Therefore, pus or an abnormal discharge is often seen on the skin, the hair under the tail, or where the dog lies.

Fever, lethargy, anorexia, and depression may or may not appear.

If the cervix is ​​closed.

The pus cannot drain outward, so it accumulates in the uterus , causing abdominal dilation. The bacteria release toxins, which are absorbed into the bloodstream, making bitches with closed pyometers seriously ill and have anorexia, apathy, depression, vomiting and diarrhea.

The toxins released by the bacteria affect the kidney’s ability to retain fluids . This is what causes the increased urine production and, consequently, the increased thirst of the bitch, who needs to drink more in order not to become dehydrated. These symptoms (increased thirst and urine) can occur in both the open and closed pyometra.

How canine pyometra is diagnosed

In the early stages of the disease , the dog may have a slight vaginal discharge and show no other symptoms. But as the disease progresses, other symptoms appear.

Pyometra should be suspected if the bitch has a recent history of heat and drinks more water than usual , especially if this is accompanied by vaginal discharge and a painful and enlarged abdomen .

Bitches with pyometra usually have high levels of white blood cells and often have a high concentration of globulins in their blood (proteins associated with the immune system). Instead, the concentration in the urine is usually low, due to the toxic effects of bacteria on the kidneys. However, these symptoms may also be due to a bacterial infection , so they are not determinative in diagnosing a canine pyometra .

If the cervix is ​​closed, an x-ray of the abdomen will reflect the enlarged uterus . Ultrasound is used to differentiate it from the uterine enlargement typical of a normal pregnancy . Ultrasonography shows an increase in the size of the uterus, a thickening of the uterine walls, and fluid accumulation within the uterus.

If the cervix is ​​open , there will often be so little uterine enlargement that the radiograph will be inconclusive .

Canine pyometra treatment

Canine pyometra requires urgent veterinary attention , since if the treatment is not carried out quickly, the consequences can be fatal for your dog, who could suffer septicemia (generalized infection), a ruptured womb or other pathologies derived from her situation.

The most common treatment is the surgical removal of the infected uterus and ovaries , using an ovariohysterectomy . This surgery requires general anesthesia.

If the disease is diagnosed in its initial stage, the surgery is less complicated than if the pyometra is in an advanced phase. In the latter case, hospitalization will be longer and intravenous fluids will be required to stabilize the dog before and after surgery.

Antibiotics are usually given for two weeks after surgery.

My bitch is valuable for breeding. Is there an alternative to sterilization?

As an alternative to ovariohysterectomy, to preserve the reproductive potential of the bitch, and provided that the pyometra is open-necked and the bitch is not infected , the administration of antibiotics and prostglandins can be resorted to .

The success rate of treatment with prostglandins is variable and is not without risks and possible long-term complications .

The prostaglandins are some hormones that reduce the level of progesterone in the blood, relax and open the neck of the uterus and stimulate uterine contractions. In this way, bacteria and pus are removed.

They are administered by subcutaneous injection for three or five days. If the evacuation is not complete, the treatment is repeated once more.

The risks and limitations of the administration of prostglandins are the following:

  • Prostglandins have side effects, such as restlessness, panting, vomiting, defecation, salivation, or abdominal pain. These side effects occur within a few minutes of administration and can last for a few hours. They become milder in successive treatments and the pain may decrease if the dog walks or exercises for about 30 minutes after the injection.
  • Clinical improvement begins after 48 hours, so that seriously ill bitches that need immediate treatment are not candidatesfor this option.
  • The use of prostglandins is not recommended for small breed bitches.
  • Since prostglandins cause the uterus to contract, it may rupture and spill infection into the abdominal cavity, which can lead to peritonitis, which would be life-threatening for your dog. This is more likely to occur at the pyometra with the cervix closed .
  • The use of prostglandins to treat pyometra have variable success rates. Bitches suffering from pyometra have a higher risk of suffering from it again in later heat cycles. To maximize their fertility chances, they should be paired in the first estrus after recovery.

Your vet will help you select the most appropriate treatment for your dog, depending on her specific situation.

What can I do to prevent canine pyometra?

Canine pyometra occurs more frequently in bitches over 6 years old who have not had puppies, and also in those who have received hormonal therapy with estrogens or progestins.

If your dog is not going to be used for breeding , early sterilization is the best way to prevent canine pyometry .

Bitches that give birth rarely or never develop pyometra. For unknown reasons, pregnancy has a protective action on the canine endometrium , preventing the pyometra from developing in the areas of the endometrium where the placenta has been attached.

Normally, a bitch goes into heat every 6 to 7 months. If your dog is not spayed , it is a good idea to keep track of the heat dates by writing them down on a calendar. In this way, you can determine if each bleeding occurs on the scheduled dates. Otherwise, you should go to your vet.


  • Canine pyometra is an inflammation of the uterus that can have serious consequences for your dog.
  • It is due to the hormonal changes produced during the reproductive cycle.
  • It appears that bitches older than 5 or 6 years who are sexually intact are more likely to suffer pyometra.
  • Cystic endometrial hyperplasia is a prerequisite for the development of the pyometra.
  • Pyometra may be caused by the entry of vaginal bacteria through the uterus.
  • The pyometra can be open or closed cervix.
  • Progestin and estrogen treatments can cause pyometra to your dog.
  • The diagnosis is based on an x-ray combined with an ultrasound.
  • Treatment involves removal of the infected uterus and ovaries.
  • If your dog is valuable for reproduction, you can resort to a treatment with prostglandins.
  • Prostland treatment has risks and limitations.
  • Previous pregnancies appear to protect against pyometra.
  • If you don’t want your dog to breed, the best prevention for canine pyometra is early spaying.
  • Go to your vet urgently if you think your dog may have a pyometra.


by Abdullah Sam
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