Dog: Pyometra

General information

Other common/scientific names: infected uterus, endometritis, pus-filled uterus

The word pyometra is derived from pyo meaning pus and metra meaning uterus. Therefore, pyometra means pus filled uterus or an infected uterus. There are two different kinds of pyometra: open cervix (open pyometra) or closed cervix (closed pyometra). Typically, dogs with a closed cervix pyometra are much sicker. However, pyometra can be a life threatening condition with either type since bacteria and toxins can leak across uterine walls and into the bloodstream. Pyometra must be treated promptly and aggressively.

Abb. GGTFMX8F: Schematic illustration of the sexual and urinary organs of the female dog.


Pyometra is most commonly seen in middle-aged to older dogs. It is a result of hormonal changes in the uterus. During estrus (heat), white blood cells are removed from the uterus to allow sperm to move through the uterine lumen. Without infection fighting white blood cells, the uterus is more prone to infection. During estrus (heat), progesterone levels elevate and remain elevated for 8-10 weeks after estrus (heat). Progesterone is a hormone which causes thickening of the lining of the uterus in preparation for pregnancy. If a dog has repeated heat cycles without becoming pregnant, the uterine lining continues to increase in thickness until cysts are formed. The thickened, cystic lining secrets fluid which is an ideal environment for the overgrowth of bacteria resulting in a uterine infection. High progesterone levels also inhibit uterine contractions preventing the uterus from naturally expelling bacteria and fluid.


Bacteria found normally in the vagina can enter the uterus through an open cervix during estrus (heat). If the uterus is normal, the bacteria will not cause an infection. However, when the uterine wall is thickened and cystic, perfect conditions can result in bacterial growth and severe infection. Canine pyometra is not contagious and cannot be spread by mating.

Cardinal symptom

  • Open pyometra: vaginal discharge
  • Closed pyometra: depression


The clinical signs of pyometra will vary depending on the whether it is an open pyometra or closed pyometra. With an open pyometra, a yellow, foul smelling vaginal discharge is usually present. Many times, these dogs are acting, eating and drinking normally. With a closed pyometra, no vaginal discharge is evident. These dogs act sick. They are depressed and have a poor appetite. Vomiting and drinking an excessive amount of water are common signs.

Abb. GFKWB6UM: Vaginal Discharge.
This is a picture of a dog with an abnormal, yellow vaginal discharge indicating pyometra.


A tentative diagnosis can be based on the history of a recent heat cycle and clinical signs. Bloodwork should be performed to support the diagnosis and give an indication of the severity of the condition. A complete blood count (CBC) can reveal an elevated white blood cell count. The uterus is enlarged and distended with pus like fluid in most pyometras. Therefore, abdominal radiographs and ultrasonography enable the veterinarian to visualize the size and condition of the uterus. Ultrasonography can provide the best image of the uterus, allowing the veterinarian to record the amount of fluid in the uterus and the thickness of the uterine wall. These determinations also aid the veterinarian in choosing the best treatment protocol.


Treatment options depend on whether the pyometra is open or closed, the clinical condition of the dog and whether or not the owner chooses to maintain a breeding female.

Closed Pyometra

Because a closed pyometra is a life threatening condition, an emergency ovariohysterectomy (spay) is the most common treatment. Prior to surgery, the dog is placed on intravenous fluids and antibiotics. The surgery is performed and typically the dog is hospitalized to provide monitoring, pain control and antibiotic therapy. Most dogs will need to wear a special collar (E-collar) to prevent them from licking their abdominal incision until the skin sutures are removed.

Abb. GFKWE5EE: Canine Pyometra.
This is a picture of an enlarged, pus-filled canine uterus taken at the time of surgery.

Open Pyometra

In the case of an open pyometra, special hormones called prostaglandins can be given to contract the uterus and enable the fluid/pus to be expelled. The female is also administered antibiotics and hospitalized. Repeated ultrasounds are used to determine the size and condition of the uterus in response to therapy. Treatment with hormone injections can be painful and result in long hospital stays.


Prognosis is good if the pyometra is diagnosed and treated early in the disease, before the dog becomes septic and toxic. However, if the condition is not detected until the female dog is quite ill with septicemia and toxemia, then a guarded prognosis is given.


Spaying is the only prevention for this condition.


It is important that all dog owners be aware of the risk of pyometra if they leave their female dog intact or unspayed. Unspayed dogs should be observed closely at 8-10 weeks after the heat cycle for any signs of pyometra. Pyometra can be a life threatening condition resulting in the death of their dog. Treatment can be painful, lengthy and expensive.

Update version: 4/24/2014, © Copyright by
Join the discussion!
3/21/2014: Ashley
I need to know something, if im already getting my girl fixed should everything be fine she is booked in with the vet to have a spay done in april cause she is only 5 months right now and we are seeing many signs of this issue in her.

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