Pyometra in Dogs

Picture of a Husky running in a field

Pyometra is a uterine infection that can occur both in dogs and in cats and that can make pets extremely ill. In this article, we will look at some of the causes of pyometra, its clinical signs, how it is diagnosed, and how it can be treated. We’ll also include some information about whether this disease can be prevented or not.

What Causes This Illness?

For many years, pyometra wasn’t completely understood. It is generally acknowledged that both estrogen and progesterone, along with their receptors, play a part in the development of the medical condition. Nevertheless, the infection per se is caused by bacterial involvement.

The problem is that while pyometra is usually caused by bacteria, we don’t know which ones and where they come from. They could be from an ascending infection in the vagina, from fecal contamination, or from a concurrent urinary tract infection.

So, why don’t female dogs develop pyometra more often, if it’s so easy for germs to get into their uterus? Well, there are cyclical hormonal imbalances that influence a female dog’s uterus and make it go through physiological changes. If the bacteria get into the uterus at a particular time during the female dog’s cycle, the hormonal regulation of the uterus will effectively allow the infection to begin.

This typically happens following estrus. If the female dog’s eggs haven’t been fertilized, there will be a higher concentration of progesterone in her blood flow, causing the lining of the uterus to thicken. If this happens time and again (meaning she doesn’t get pregnant), she could develop a condition by the name of cystic endometrial hyperplasia. Should this occur, the uterus lining would secrete plenty of fluid, which creates a perfect environment for bacteria to thrive in. In case you didn’t know, a healthy uterus doesn’t normally have a lot of fluid in it, which means that it’s very difficult for bacteria to reproduce there.

There are other causes of pyometra. People often use progestational compounds so as to delay or suppress the female dog’s estrus altogether – in this way, she isn’t going to be able to sustain a pregnancy. Administration of estrogen is also done following mating, in case a female dog is mismated. Last, but not least, the bacteria could travel into the uterus from the male dog’s semen and secretions following copulation.

Some of the most common types of bacteria isolated in cases of pyometra are Escherichia coli, Staphylococcus, Streptococcus, Proteus, and Pseudomonas spp.

Clinical Signs

The symptoms of pyometra can be somewhat variable. Some female dogs experience lethargy, polyuria, polydipsia, anorexia, or vomiting. If the cervix is open, pet parents could notice a purulent discharge (pus-like); if the discharge contains traces of blood, the dog owner might just mistake it for a normal estrus.

If the cervix is closed, the infection (and the pus) accumulates inside the uterus, causing abdominal distension. This is a very critical situation where the animal sometimes has a fever, is very lethargic, and experiences dehydration. If the cervix is patent, a bloody to mucopurulent vaginal discharge will be present. Since just about 20% of affected female dogs have a fever, it’s not a truly reliable clinical sign.

Unfortunately, most pets that develop pyometra and aren’t brought in for an examination fast enough will go into septic shock. The bacteria effectively release toxins into the bloodstream, which is why dogs that have a closed cervix will become severely ill in a remarkably short amount of time. Female dogs suffering from pyometra are listless, depressed, and won’t consume food.

How Is Pyometra Diagnosed?

Because of its frequency and severity, pyometra is a medical condition that should be suspected in any unspayed female dog. If symptoms such as vomiting, the dog drinks too much water or ‘goes to the bathroom’ too often are present, a pyometra diagnosis should definitely be considered.

The diagnosis can be set using the animal’s medical history, physical examination, ultrasonography, as well as abdominal radiography. If there is enough time for it, vaginal cytology can determine the exact nature of the vaginal discharge. A biochemical profile, urinalysis, as well as hematological tests, can be performed, as well. These all help with the exclusion of other causes of vomiting, polyuria, and polydipsia. Besides, they can offer valuable information with regard to how the animal’s kidneys are functioning or whether there’s any risk of septicemia. There is also the option of collecting a uterine exudate, examining it, and performing sensitivity tests.

Although there are a lot of diagnosing methods that can be used in a pyometra case, sometimes the vet will have to act fast and choose the appropriate treatment as quickly as possible. The female dog’s life can be in danger, especially if the cervix is closed and ultrasonography has revealed that she has pyometra.

How Is Pyometra Treated?

Given that pyometra is a medical emergency that needs rapid intervention so as to prevent even more severe infection and death, it first calls for preoperative stabilization. After the animal has become stable, spaying the female dog is the elected therapy in the vast majority of cases. This kind of treatment typically ensures rapid recovery with minimal risk of the issue recurring. Furthermore, ovariohysterectomy makes it impossible for the female dog to develop ovarian or uterine cancer or experience any unwanted pregnancies in the future.

There is another way of treating pyometra, and it usually involves the use of injectable antibiotics and prostaglandins. The reason this is a less preferred therapy among veterinarians is that it can take up to several days for the medications to have an effect, which means that the dog might have to experience all of the symptoms for some time more. This includes a high heart rate, salivation, breathing difficulties, fever, panting, severe abdominal pain, as well as excessive vomiting and defecation. Even in cases when the female dogs have a breeding value, this is a very high-risk therapy to choose as the dog can lose her life by the time the hormonal and antibiotic treatment actually does something. Plus, prostaglandins aren’t even approved in the United States for use in dogs and cats.


If the pet parent decides to choose the therapy that involves medication instead of surgery, there is a possibility that the animal recovers. However, because the uterus isn’t removed, recurrence is likely. Almost 70% of female dogs that have had pyometra and were treated for it will experience it again over the course of 2 years following the treatment. That’s why it is highly recommended for these female dogs to be bred until the desired number of puppies were produced, and then they should be spayed.

Prostaglandins are very risky and could make the clinical signs of pyometra even more severe, along with a series of side effects that they have. Because they are dangerous, it is advised to avoid giving them to pet owners to administer to the dog.

The prognosis for survival with ovariohysterectomy is from 80% to 100%. All that it matters is that any abdominal contamination is avoided and that the infection is also treated with antibiotics. If sepsis is installed and organ failure is developed, the prognosis can be significantly less favorable.


This section is going to be very short. The only effective way of preventing pyometra is to spay your female dog. Even if the spaying procedure does not involve the removal of the uterus, the fact that the dog will not have ovaries any longer means that there is not going to be a hormonal effect on the uterus. Therefore, the lining won’t allow a bacterial infection to develop as easily as it would in an animal that wasn’t spayed.

Furthermore, the cats and dogs that have been spayed early in their life are at an even lower risk of developing pyometra, along with any other diseases pertaining to their reproductive system (including cancer).



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