Pyometra is a serious and potentially life-threatening infection that affects intact (i.e., unspayed) female pets. Unfortunately, many pet owners don’t realize their unspayed pets are at risk for this condition. Our team at The Pony Express Veterinary Hospital explains what every pet parent needs to know about this dangerous condition, including the cause, signs, treatment, and prevention.

What causes pyometra in pets?

Pyometra—Latin for “pus-uterus”—is a uterine infection that results from hormonal changes in a female pet’s reproductive tract. After a female goes through her heat cycle, elevated levels of the hormone progesterone lead to changes in the lining of the uterus in preparation for potential pregnancy. However, when pregnancy doesn’t occur, the thickened uterus 

nourishes bacteria and becomes vulnerable to infection. When bacteria that normally inhabit the vaginal canal make their way into the uterus, the combination of a hormonally primed environment and bacterial invasion results in pyometra, where the uterus fills with pus. Pyometra in pets can take two forms, including:

  • Open pyometra — During an open pyometra, the cervix (i.e., the tube that connects the uterus to the outside world) remains open, allowing the fluid to drain.
  • Closed pyometra — During a closed pyometra, infected contents are trapped by the closed cervix. Because a closed pyometra causes no discharge, it can be more challenging to identify until a pet is in critical condition.

Which pets are at the most risk for pyometra?

Any intact female pet is at risk for pyometra, but the risk goes up with the increasing number of heat cycles a pet has. That means the older your intact female pet, the greater their pyometra risk, because their uterine lining can thicken excessively or develop cysts, providing an ideal environment for the infection. Pyometra commonly develops one to two months after a typical heat cycle.

Why is pyometra in pets dangerous?

Without timely intervention, pyometra can be life-threatening. As a pyometra infection progresses, the uterus becomes increasingly distended, and a pet’s body responds with a surge of white blood cells and other inflammatory markers, potentially leading to septicemia, a systemic infection. A closed pyometra is especially dangerous because the pus has no outlet, increasing the risk of the uterus rupturing. A ruptured uterus can spill its infected contents into the abdominal cavity, causing peritonitis, a severe and often fatal inflammation. Toxins and bacteria from the infection also can enter the bloodstream, leading to septic shock, organ dysfunction, and death. 

What are the signs of pyometra in pets?

Pyometra requires immediate veterinary attention, so it’s important to recognize the signs. Signs generally appear around four to eight weeks after a pet’s heat cycle ends and may include:

  • Lethargy
  • Excessive thirst and urination
  • Depression
  • Pale gums
  • Appetite loss
  • Bloody or milky vaginal discharge
  • Vomiting
  • Diarrhea
  • Abdominal swelling or pain

Because some pets show only vague, non-specific signs, pyometra should be considered for any unspayed sick female pet. If your pet displays pyometra signs or seems to be ill one or two months after their heat cycle, seek immediate veterinary care at The Pony Express Veterinary Hospital. 

How is pyometra in pets treated?

Pyometra is a veterinary emergency, and affected pets require rapid intervention to prevent overwhelming infection and death. If your veterinarian suspects a pyometra, they will first examine your pet for visible signs such as abdominal swelling and discharge. They also may recommend diagnostic testing (e.g., blood work, urinalysis, or vaginal cytology) to identify infection and inflammation and X-rays or ultrasound imaging to visualize the uterus’ condition (e.g., thickness, contents, or inflammation).

Pets with suspected pyometra are often in critical condition and likely will need emergency surgery to remove the ovaries and uterus, which eliminates the hormonal influence that led to the problem and the infection. While pyometra surgery is similar to a routine spay, the infection makes the surgery more difficult. Most pets who are promptly treated surgically survive, but some could experience serious infections and die. Pets are hospitalized for several days following their surgery for observation, antibiotics, IV fluids, and other supportive care.

How can pyometra in pets be prevented?

The only way to protect your pet from pyometra is to have them spayed. Female cats should be spayed before their first heat cycle, which occurs around 5 months of age, and female dogs should be spayed between 5 and 15 months of age, depending on their breed and lifestyle. A spay procedure also is recommended to protect older pets from pyometra. Our veterinary professionals can help you determine the appropriate time to spay your female pet.

Contact The Pony Express Veterinary Hospital team to discuss the right time to spay your pet and help ensure they never suffer from a pyometra.