Pyometra in Dogs

A study shows which antibiotics are most often prescribed for this bacterial infection.


Pyometra is a bacterial infection of the dog’s uterus. It can be life-threatening and requires prompt veterinary attention. It occurs in unspayed dogs although, rarely, in a spayed dog. If it occurs in a spayed dog, it’s because a small piece of uterus remained after the spay and that is still susceptible to infection (this is called “stump pyometra”).


Symptoms of pyometra in dogs include:

  • Increased water intake
  • Lack of appetite
  • Lethargy/weakness
  • Fever
  • Vomiting
  • Painful abdomen (may be distended)
  • Possible purulent discharge from the vagina

Causes of Pyometra

Pyometra develops when infectious bacteria invade the uterus. This is most common shortly after a heat. The cervix is loose during a heat, so bacteria easily gain access to the uterus, and the uterine lining is built up enough during heat to provide the perfect growth medium for bacteria, E coli in particular.

Diagnosis of Pyometra in Dogs

Diagnosis is generally done via a veterinary exam with palpation of the abdomen followed by radiographs or ultrasound. The uterus will appear distended. Bloodwork, especially a complete blood count (CBC), will indicate an infection.

Antibiotics to Treat Pyometra

Since it’s a bacterial infection, antibiotics are prescribed. While it’s preferable for the veterinarian to do a culture and sensitivity test to choose one, time is often of the essence, so your veterinarian may make the decision based on what has worked well in the past.

The most commonly used antibiotics, according to a survey of 152 veterinarians, published in Veterinary Medicine and Science (May 2023), are:

  • Amoxicillin/clavulanate potassium (86%)
  • Enrofloxacin (52%)
  • Cefazolin (37%)
  • Ampicillin/sulbactam (22%).

Closed Pyometra

Some dogs will have “closed pyo,” which means the cervix is tight enough to prevent any discharge. This can complicate both diagnosis and treatment.

The most common treatment for this is an ovariohysterectomy or spay. Note: This surgery is more complicated than a standard spay because the dog’s uterus is swollen with pus and the tissues are friable and fragile. In addition, the dog is fighting systemic illness from a serious infection. She will need to be on IV fluids, monitored carefully throughout surgery and post op, and receive antibiotics to fight the infection.

Open Pyometra

In “open pyo,” the cervix is not closed and the purulent material is draining out. In these cases, medical management with the use of prostaglandins may be attempted. This is most common with a valuable brood bitch whose owners would like another litter. If medical treatment is not successful, surgery is necessary.