Pyometra is a potentially life threatening infection that occurs in older female dogs that have not been spayed. Originally it was believed the condition was only an infection in the uterus that was caused by bacteria. Now we know it is actually caused by a hormonal imbalance in which the female dog’s body produces too much progesterone or there is an abnormal sensitivity that occurs to normal levels of the hormone.
When this occurs the lining of the uterus becomes filled with cysts. These cysts can be very large and produce a lot of fluid that collects in the uterus and causes thickening of the entire organ. Even the ovaries and the uterine horns will swell to several times their normal size, putting downward pressure on the entire organ. This in turn causes a leakage from the vagina that may be mistaken for the female coming into heat. The licking of the discharge by the dog and the presence of the fluid also creates the possibility of a secondary bacterial infection that only produces more fluid in the cells of the vagina and uterus. In response to the infection the cervix closes and all this liquid and bacteria is trapped. The swelling becomes extreme and the dog will be in considerable distress and pain.
At this time the dog will also change her behavior. She will become very tired and lethargic and go off her food. She will drink excessively and urinate frequently. Typically the discharge from the vagina is white and, once this stops, she may seem unable to move her hind quarters or to get up.
In rare instances the pressure can build and cause the uterus to rupture. When this happens death occurs within one to two days. However, more commonly the excessive amount of fluid is removed through the circulatory system. This puts additional demands on the kidney and the high levels of toxins in the blood result in kidney failure and a fatal condition known as uremic poisoning.
The good news is that pyometra is completely preventable with spaying. Females that have been diagnosed and treated once for pyometra should be spayed as soon as possible. Treatment for pyometra needs to be aggressive and early in the onset of the condition before serious kidney damage occurs. It will require hospitalization and treatment with antibiotics and medications for several days before the dog can be released to the home.