FaceBook    Instagram   

Pyometra (Uterine Infection)

Education > Dog Health & Behaviour 1st April 2019


Pyometra is a bacterial infection in the uterus. This is a potentially life-threatening disease and often occurs in older, unsterilised female pets after oestrus. Pets with pyometra will become systemically unwell and show signs such as fever, depression, lethargy and vomiting.

Diagnosis of pyometra is often based on clinical signs and history. A senior unspayed female who recently came in heat, with vaginal discharge and an enlarged abdomen should be suspected of having pyometra. Radiographs and ultrasound will show a distended fluid-filled uterus. A complete blood count often shows an elevated white blood cell count.

Pus accumulates in the uterus causing the abdomen to be distended. Major surgery is often required to remove the entire infected uterus and ovaries. The surgery is more challenging than a routine sterilisation due to the infection. Antibiotics are given for 1 to 2 weeks post surgery.

Non-surgical treatment or medical therapy may be offered in rare situations where surgery cannot be performed (e.g. old age or ill health). However, the chance of successful treatment is low and the rate of recurrence is high. In addition, there is a risk of uterine rupture and spillage of infection into the abdominal cavity.


  • During a heat cycle, the lining of the uterus thickens in preparation for pregnancy and foetal development. Over several estrus cycles, the lining increases in thickness and cysts form within the tissues - a condition known as Cystic Endometrial Hyperplasia. The abnormal womb is prone to infection.
  • Bacteria normally found in the vagina can enter the uterus via an open cervix during a heat cycle. If the uterus is thickened and cystic, it is an ideal environment for bacteria to grow.
  • Use of progesterone-based drugs also causes a thickening of the uterus lining.


If the cervix is open, pus will drain out resulting in yellowish or blood-tinged discharge on the floor, bedding or fur around the vulva. Dogs with open pyometra often lose their appetite and may be listless or lethargic.


If the cervix is closed, pus is unable to flow out of the body. It accumulates in the uterus and results in a distended abdomen. As toxins build up within the body, the patient can become ill very rapidly.

Besides preventing pyometra, there are other medical and behavioural benefits in sterilising our pets.