Can a Spayed Dog Get Pyometra?

Pyometra is more specifically an infection of the uterus^[1]. It presents itself with the secretion of pus, distention and other systemic changes. The uterus and ovaries make up the female reproductive system of a dog. Its cycle consists of four phases, perhaps the most obvious one being the estrous cycle known as the dog ‘being in heat’. During this period, the uterus opens which allows for bacteria to enter through the vagina. The cycle after the estrous cycle is called the metestrus or diestrus cycle. During this period the uterine tissues undergoes changes and the presence of the hormone progesterone increases. If these changes are accompanied by an inflammation of the endometirum (the inner lining of the uterus), the uterus will become a very suitable habitat for bacteria. Additionally, the uterus will close and keep this bacteria in.

All of this explains why pyometra can appear after the heat stage, usually about 2 to 3 months later. It is characterized by a nonspecific symptomatology. This means it has symptoms common to other pathologies such as polydipsia (increased water intake) and polyuria (increased urination). These symptoms include vomiting, anorexia, lethargy, reluctance to jump, abdominal pain fever and sometimes bloody vaginal discharge. This last symptom can sometimes get confused with normal aspects of being in heat, especially with open pyometra.

There are two types of pyometra, open and closed. Open pyometra means the cervix is open and the infected material can leave the body. Closed pyometra is when the cervix is fully closed, so the infection stays inside, building up pus and discharge which can potentially rupture (potentially leading to peritonitis). However, if the disease occurs during the period of heat in dogs, does this mean spayed dogs can't get pyometra?

To help us answer the question proposed in this article, we need to look at some of the different types of sterilization:

• Tubal ligation: this technique is not generally recommended because its only benefit is to prevent the dog from getting pregnant. A bitch would still maintain its heat cycle and is susceptible to the health problems which can occur.
• Hysterectomy: extraction of the uterus only. This is not generally recommended either as the action of the hormone production caused by the ovaries will still occur and can negatively affect the dog's psychology.
• Oophorectomy: this is the removal of one or both of the ovaries and it interrupts the heat cycle. If performed between the first and second heat it can potentially help prevent breast cancer in dogs.
• Ovariohysterectomy: this intervention removes both the uterus and ovaries and is commonly known as spaying. Due to the full removal, there will be no hormonal action, estrous cycle (heat cycle) or uterine tumors. This is why it is the most frequent procedure carried out when sterilizing dogs.

As we can see, just because a dog has been sterilized, doesn't mean that it can't get pyometra. This is because it depends on the type of sterilization carried out. Spaying should remove the entire uterus meaning the infection can't occur in the first place.

Whether we adopt the bitch or have the procedure carried out from puppies under our care, we need to consult with the vet to know what type of operation has been or will be carried out. In these cases, the key to understanding whether a spayed dog can get pyometra is whether they have something known as a remnant. This is when there is still the presence of ovarian tissue, despite both ovaries ostensibly being removed. If it happens, it is often due to the surgical technique as it can be difficult to reach certain areas due to the dog's physiology. Also, it is possible for the ovarian tissue to stay lodged in the abdominal cavity and, due to the presence of hormones, become revascularized and functioning like a regular ovary.

In this latter case, the activation of the hormones produced in the ovarian remnant causes the pyometra. This is known as stump pyometra. Vaginal bleeding or any symptomatology like the one explained in the previous section requires urgent veterinary consultation. Although young female dogs can develop this condition, it is especially important to keep an eye out for this happening in adult dogs over 6 years of age. This is because the risk increases in older dogs.

In conclusion, pyometra will occur in the following circumstances:

• When the dog has not been spayed.
• When a portion of the uterus remains in the body after spaying.
• When the hormone progesterone is elevated due to an ovarian remnant (endogenous) or by certain medications (exogenous).

We have already seen that a sterilized bitch can contract pyometra, whether they have been spayed or not. However, it is also important to remember that pyometra caused by ovarian or uterine remnants aren't as likely. This means, you need to ensure you take the dog to a vet so that they can ensure the above symptoms are not due to a different pathology. Most sterilized bitches will be at low risk of this condition.

Top confirm the presence of pyometra, the vet or specialist will take an x-ray or, better yet, perform an ultrasound. Furthermore, a blood test should be carried out to see if these is an increase in leukocytes (white blood cells which increase during the presence of an infection). They will also check for anemia and renal function. This is because pyometra can affect the production of creatinine and urea due to toxins created by the E. Coli bacteria. This is the most common root cause of pyometra.

Its expansion is a risk in a dog as it can poison the blood and lead to septicemia (a generalized blood infection). Once the condition is diagnosed, the most common method of treatment is a combination of surgery and antibiotics. Before operation the dog needs to be stabalized. This means they require adequate fluid and anaesthesia. It may be possible that pyometra can be treated with medicine only, but this leaves it open for the infection to return.

The operation is risky as the uterus, under these conditions, can tear which can lead to shock and, potentially, death. For this reason, pyometra is a potentially fatal condition. Prevention, by means of sterilization, is perhaps the most effective measure to avoid the disease. As we stated, even with spaying, the probability of not contracting isn't 100%.

In conclusion, after spaying, a female dog can still have a stump pyometra (remnant) as a complication of surgery. Other complications of the spaying procedure include:

• Bleeding during surgery, especially if it takes place during the estrous heat cycle as there will be a greater blood supply to the uterus.
• Sometimes the urethra can be accidentally ligated.
• Urinary incontinence due to adhesion between the bladder and uterine stump (or even due to increase of estrogen).
• Fistulas caused by inadequate suture material.

All of these risks are minimized with proper surgical technique, hence the importance of a good veterinarian who will make the appropriate referral. The instances of complications is low enough for spaying to be generally recommended for female dogs.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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