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Pyometra in Dogs

pyometra in dogs


Pyometra is an infection of the uterus that commonly affects intact, middle-aged dogs. This condition can be life-threatening for dogs so early diagnosis and treatment are imperative for a better outlook for the pet.

Pathophysiology of Pyometra in Dogs

The cyclical reproductive cycle of a dog brings about hormonal changes in its body to prepare for a possible pregnancy. Specifically, progesterone levels remain elevated even after estrus to facilitate the thickening of the uterine wall. Year after year, these dogs go through the same changes but as the dogs grow older, the uterus may have some permanent changes. With the continued development of the uterus, there are increased secretions, making it conducive for bacterial growth.

The bacteria, Escherichia coli, cultured from the uterus of dogs suffering from pyometra is consistent with those often found in the vagina and intestines. This finding leads to the conclusion that in some cases, pyometra may develop from ascending infection of the vagina, or urinary tract, as well as fecal contamination. This kind of infection usually becomes evident 2-3 months after the dog’s estrus cycle.

Spaying the dog early in its life can prevent a pyometra. However, in rare instances, an incomplete ovariohysterectomy can leave behind a uterine stump which could get infected.

Pyometra in dogs is categorized as open or closed. An open pyometra occurs when the cervix is open, causing infectious materials to leak out of the body. Pet owners will often notice purulent vaginal discharges or discoloration of the dog’s fur near the vagina. A closed pyometra, on the other hand, occurs when the cervix remains closed so infectious materials are not discharged and they build up within the uterine walls.

Signs and Symptoms

Dogs with pyometra exhibit a distended abdomen that’s usually painful to touch. On top of this, the dog is also lethargic and depressed. It tends to lose its appetite but urinate and drink frequently. Some dogs may have extensive symptoms, which include diarrhea, vomiting, and weight loss while some dogs don’t exhibit symptoms other than vaginal discharge with the presence of pus.

In severe infection, signs may not be limited to the genital tract. Bacteria may release toxins, which could lead to sepsis, a life-threatening condition for the pet.


Diagnosing this condition often starts with the veterinarian asking for the medical history and performing a physical exam of the dog. Pet owners will be asked questions about the symptoms and their onset. After this initial check-up, the vet may also request several diagnostic tests, such as:

CBC and Urinalysis

These basic lab works will indicate if there’s an infection and evaluates acid-base status, renal function, and septicemia. A spike in white blood cells is indicative of an infection. The results of these tests will also rule out other possible causes of polyuria (frequent urination) and polydipsia (frequent drinking). Upon reading the results of these tests, the vet can decide if the pet is in dire need of IV fluids or other interventions to stabilize its condition.


Abdominal radiography and ultrasound may be needed for the vet to have a visual of the infected uterus. Comparatively, radiography costs lower than ultrasound but its result could be merely suggestive whereas, ultrasound allows for a more definite identification of the condition.

Vaginal Cytology

This procedure is particularly helpful in open pyometra in dogs. The result of this diagnostic test will only indicate the stage of the estrus cycle for those with closed pyometra.

To perform this procedure, a vaginal smear is obtained from the dog and subsequently analyzed under the microscope. Increased number of degenerate neutrophils, as well as extracellular and intracellular bacteria, may be indicative of pyometra. However, the same can also be said of other reproductive infections like vaginitis so further testing might be needed for final diagnosis.

Bacterial Culture

Bacterial culture of urine and uterine contents may also be recommended so that antibiotic susceptibility testing may be performed. This is to empirically test the efficacy of antibiotic therapy.


Initial treatment is always focused on stabilizing the dog especially if it is exhibiting severe symptoms. To do this, the vet may order IV fluid therapy to restore electrolyte balance, keep the dog hydrated, and replace essential nutrients. In some cases, the vet may also administer parenteral antibiotics.

Surgical Treatment

Surgical removal of the uterus (ovariohysterectomy) has always been the treatment of choice for this condition. This treatment option is more curative and lessens the risk of recurrence compared to medical management.

However, ovariohysterectomy is not without considerable risks. Removing the uterus due to pyometra is riskier than the regular spay operation. Dogs with pyometra have a fragile uterine wall so there’s always the possibility that the uterus may rupture during operation and infectious materials may spill over to its abdomen. When this happens, the surgeon will extensively wash out the leakage using a warm saline solution.

Other complications like cardiac arrhythmia, aspiration pneumonia, and hypotension could arise during the operation as well. This is why pet owners have to proactively ask for a discussion with the veterinarian when considering this procedure. After surgery, the dog may develop fistulous tracts, wound infection and swelling, as well as hemorrhage.

Medical Management

Dogs without other severe illnesses can be treated successfully with just medical management. Pet owners who don’t want to subject their dogs to surgical risks or those who don’t want to make their pets sterile opt for this treatment. However, dogs with closed-cervix pyometra run the risk of a ruptured uterus due to the continuous build-up of infectious material.

The goal of this approach is to reduce the stimulation of progesterone in the uterus. To achieve this, the vet will prescribe medications that either block progesterone receptors or prevent the corpus luteum in the dog’s ovaries from producing progesterone. Common types of drugs used for these purposes are prostaglandins, progesterone receptor antagonists like aglepristone, as well as dopamine agonists like bromocriptine and cabergoline. It is important to note, however, that prostaglandins are not approved in the United States for canine and feline use.

Dogs that undergo medical therapy must be closely monitored during treatment and the days or weeks after treatment. During this time, the dog’s vaginal discharge, mental health, and vital signs are often evaluated. Furthermore, pets that went through medical treatment for pyometra have a greater risk of developing pyometra again. When this happens, surgical treatment is the most viable recourse.

Outlook and Recovery

Prognosis highly depends on the occurrence of complications. Animals that didn’t have a ruptured uterus and didn’t develop a systemic infection, have a very good prognosis. The mortality rate is about 5%. Deaths are often due to secondary shock or endotoxemia.

Once discharged from the hospital, the dog usually needs just minimal aftercare. The veterinarian will most likely prescribe antibiotics to be administered for up to a maximum of 10 days. The aftercare is generally the same with a dog that went through a spay operation. Pet owners must see to it that the incision is safe from trauma due to excessive activity.

Dogs with pyometra generally have a good outlook. However, pet owners who don’t want to deal with the prospect of having their dogs go through surgery or the taxing medical treatment have a very good reason to spay their pets while they’re still young.

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