Pyometra in Cats and Dogs

A trip to the veterinarian with your sick cat or dog has led to the diagnosis that your beloved pet has a pyometra. What does this mean? The word pyometra can be broken down into pyo and metrum which are Latin for ‘pus’ and ‘uterus’, respectively. As the derivative of the word suggests a pyometra is the accumulation of pus inside the uterus. Since a pyometra is an infection of the uterus it can only affect un-spayed female dogs (bitches) and cats (queens). Dogs tend to get pyometras more commonly than cats and risk increases with age. Pyometras can happen regardless of whether the animal has been bred or what heat cycle she is in.

Pyometras generally start because of hormonal and structural changes in the lining of the uterus that make it more favorable for bacterial colonization. The bacteria, usually E.Coli, that are responsible for the pyometra arise from the vagina and ascend into the uterus. There are two different forms of pyometra which are referred to as open and closed pyometra. A pyometra is classified as open when mucus or pus is seen dripping from the vulva (the external genitals of the female). This discharge may or may not contain blood. No discharge from the vulva is seen in a closed pyometra. These two forms of pyometra depend on whether the cervix, which is the narrow, lowest part of the uterus that joins with the vagina, is open or closed (Note: during labour it is the cervix that dilates to allow the passage of the baby out of the uterus).

An open pyometra is much safer and easier to treat because the cervix is open, allowing the pus to drain from the body. This smelly discharge is often what draws the attention of the owner and causes them to bring their pet to the veterinarian. A closed pyometra, on the other hand, is a much more serious condition and is always treated as an emergency by veterinarians. In a closed pyometra, the cervix is constricted which prevents the infected material from being able to drain out of the body. As the infection builds, the uterus is at a serious risk of bursting and spilling all of the pus and infected tissue out into the body cavity where it causes sepsis and shock. Sepsis means infection of the entire body and septic shock occurs when there is decreased oxygen and blood flow to the organs as a result of infection. Septic shock eventually leads to multiple organ failure and death. Despite heroic efforts on the part of the veterinarian, an animal in sepsis may not be able to be saved.

The lack of vaginal discharge in cases of closed pyometras makes it the harder of the two to diagnose. Animals are often brought to the veterinarian for non-specific signs of illness such as anorexia, vomiting, lethargy, depression, increased drinking, and increased urination. Abdominal palpation often reveals abdominal pain and an enlarged uterus.

The most common treatment for both types of pyometra is an emergency ovariohysterectomy (emergency spay) and antibiotic therapy. An ovariohysterectomy removes the entire reproductive tract of the female animal and in the case of a pyometra removes the source of infection from the body completely. Although, this is the safest and easiest way to treat a pyometra it does mean that the animal can never be bred again. In animals that are valuable for breeding, it is possible to treat the pyometra with long term antibiotic therapy and a drug that causes the uterus to contract and push out the pus and infection. The risk of re-infection is high, however, and it is advisable to breed the animal in her first subsequent heat cycle and then get her spayed. All females that have been retired from breeding and all pet animals should be spayed to reduce their risk of developing pyometra. Although some people shy away from spaying their pets because of cost, the one to two hundred dollars it costs to spay a pet is nothing compared to the thousands of dollars an emergency pyometra can cost. Do not take the chance with your pet and budget, be a responsible pet owner and have your pets spayed or neutered.

By Melanie Youngs – Pets.ca writer